This is where the debate can get pretty heated, but one thing that is not usually contested too much is mixing stuff, you want either a power conditions/plug strip or UPS that you can plug everything in to associated with your HT, including the cable feed if you have one, ehternet if you use one, and same for a phone line as well as all of the power plugs.
UPS Option, take care to read the spec's carefully on a UPS, for example the Belkin you like has both conditioning and UPS, and has two outlets that just provide conditioning so doesn't count against your UPS load, and then the rest of the outlets are on the UPS side.
BELKIN AP30800FC10-BLK UPS -- 1,200 VA / 640W
http://cache-www.belkin.com/support/dl/p74699fc-a_ap30800fc10-blk_manual.pdf
That unit looks nice, but for your TV I think it is on the edge of what you want, it will do the job but not for all of your stuff on the UPS side, and I would make sure to get the details of its alarms for overload, it is rated at 1,200VA / 640W and if you go with that then that is all I would put on the UPS is the TV, then on the conditioning side put on a el-cheapo plug strip with no surge protection, just plugs that will give you the conditioning.
Using 2 surge protectors can do weird things, and may also invalidate the warranty and insurance offered. The only thing that I see that makes me wonder is the 640 watts total or an alarm will go off and that will be annoying, what I am not sure of is if the alarm will only go off if the UPS side exceeds 640 watts, if that is the case then the Belkin would be OK with just your TV on the UPS side and everything else on the power conditioning side. If the alarm goes off for over 640 watts for both sides, then it is too small for your system.
If you are going the UPS route and can afford it I like the APC, it is the only brand I use. It is 500 bucks, likey cheaper on eBay but look at this one:
APC -- For UPS and Conditioning 1,500VA / 1,250W
http://www.apc.com/products/apcav/products/index.cfm?action=detail&base_sku=S20BLK&tab=documentation
Finally we get to power conditioners, the most debated approach, these come in all kinds...
I use an APC UPS on my computer that is the same rating but a different model without the AV stuff, and was going to get that one for my HT but a neighbor gave me (well token charge) a Monster power conditioner when he bought a UPS for his system or I would have NEVER spent what Monster wants for these, but it is a nice unit and I run everyhing for my HT though it. Since the only thing my HT loses on a power hit is the time on the tv it made a UPS sort of a waste, the Monster deals with sags very well as well as RF, spikes, and inter-component noise, looks good also 
Monster HTS 3600 MKII -- Conditioning only -- Max 1,800W / 15A (All your wall can deliver)
In the year I have had it has tripped twice, a major SAG (cause unknown) and it had my system powered down before I even preceived the lights dimming, and who knows what happened when wind made two power lines touch, but I did have neighbors lose some electronics, most didn't and even those that did, it was spotty, they did not lose everything.
I will never really know for that event what really protected me, the whole house protector or the Monster, all I know was after the power came back on I had no damage to anything.
Just one last note, don't get anything cheap, or claims its protection is by sacraficing itself, IMHO those units are junk, you have a few grand in your system, if you are going to get a power conditioner or UPS, then get one that is on par with the rest of your stuff, but if you get anything I would suggest the whole house protection, that is money well spent.
Sorry for the information overload, but you have a big investment and you might want to do some more leg work, not just at vendor sites like Belkin others, but reviews, other unbiased sources.
First I will admit I am a tad on the overkill side when it comes to power and my HT and computer, second that the actual value of power conditioners is often a hot debate, and finally, I don't think you will like what you are about to read, but as with any advice it is there for your consideraton, take it, leave it, or take the parts you like... That said, hang on!
Overview --
Power protection/conditioning is an all or nothing deal, anything less than all is just a waste of your money. This means everything you have interconnected to your HT needs to be protected or none of it really is.
The cheapest and best way to do this is have an electrician install Whole Home Protection at your breaker panel. The actual protectors are fairly inexpensive but should be put in by a professional electrician as it means messing with the supply side of your mains as they enter your breaker panel, an easy place to end up dead if you don't know what you are doing.
What this will do is offer mostly lightening and spike protection for your entire house including your HT system. This will not help with sags (power drops), rf noise, noise/sags generated by motors on things in your house and the endless list of other things, including your HT components themselves that generate noise. This you might call Level 1 protection or basic protection, it will keep your stuff from getting fried by events on the power lines to your home, but not any more. Your components are all good stuff and should have plenty of protection in the power suppy that can deal with most other issues unless you have really noisy power.
Some will argue that anything past this is a waste of money, personally I disagree with them but if you search the forum on power you will find plenty of views on this.
Before you even consider conditioning and/or UPS, lets look at the load your components state they will use.
OK -- Now the bad news, your list of components, including the ones you either did not consider or don't have pretty much is a full load for a typical home wall circuit which is 1,800 Watts / 15A.
UPS Rating* (Act Watts) -- Device
1,000 VA (481W) -- Pro-141FD Monitor
350 VA (180W) -- HTB2SE Sub
750 VA (400W) -- VSX-21TXH Receiver
500 VA (500W) -- PS3 Game / Blu-Ray
70 VA ( 50W) -- Typical Cable Box
==============================================
2,670 VA* (1,391W) -- All in
*The VA rating for the UPS is actually a lot higher than the actual VA for the stated wattage, but they are what most UPS calculators would suggest for the actual wattage listed. (There is room to play)
Now some Good News -- Granted this is vendors stated peak, actual load is likely to be a lot lower even under extreme use. For example, my system with the TV (631W), the Receiver(475W), Blu-Ray (120W), Sub-Woofer (220W), Cable Box (50W) adds up to 1,496W or ~12.5Amps at 120VAC, but in actual fact, it is pulling between 5.5A - 6.2A with 7.1 speakers and volume pretty cranked and the picture in "game mode". Typically when I look at the Amp load it is 2-4A with just the TV, receiver, cable box, Sub, and Blu-Ray on at a reasonable volume.
Even if I hit my HT remote and power everything up at once, the highest I have seen is 7 Amps so I think the spec's are overstated intentionally by vendors, that is probably everyhing cranked to max in a room that is 110 degrees, and all really starting at the same time, my receiver comes on in two stages and so does my TV.
So you can likely figure your system will use less than 50% of the capacity of a 15A circut (7.5A) in all but the most extreme conditions.
Now a typical house has more than one outlet on a room circuit, so the place you plug in your HT system to is likely in a loop with the other outlets in that room and in other rooms, you will not know until you trip the breaker and test every thing electrical to see what is dead when that breaker is tripped. So you not only have to consider your HT load, but any lamps, appliances, and other stuff plugged in or wired to that circuit.
Options:
Best: Have a dedicated circuit run to your HT oultet, again a job for an electrician unless you know your stuff. The downside is that if you do not have a basement this can get pretty costly.
Practical: Take care of what else you have on that circuit, and remove any how power use items you can from that circuit, this is usually not too hard. What can really nail you is plugging in say a vacuum cleaner while the system is running, you will only make that mistake once as the breaker is going to go pretty quick for a typical vacuum cleaner or 1500W space heater.
That is about it for load management, your PS3 is really about the only optional component you have. I really doubt you will need to run a dedicated circuit, I did since I have a basement and could DIY so my total cost was a breaker, some romex, and a new socket, so under 30 bucks. I did have an electricial put in my whole home protector but can't remember what that ran me, it was not bad though.
Here is a list of your stuff with links to the manuals:
TV: Pioneer Kuro Elite Pro-141FD. 481W = Minimum UPS 700VA / Recommended UPS 1000VA
http://www.pioneerelectronics.com/StaticFiles/Manuals/Home/PRO-141FD_OperatingInstructions0905.pdf
Speakers: Kef FiveTwo Model 11 with HTB2SE subwoofer. 180W = Minimum UPS 260VA / Recommended UPS 350VA
http://www2.kef.com/resources/Current%20Products/Subwoofers/HTB%20Series/_manuals/htb2_manual_en.pdf
Receiver: Pioneer VSX-21TXH. 400W = Minimum UPS 560VA / Recommended UPS 750VA
http://www.pioneerelectronics.com/StaticFiles/Manuals/Home/VSX-23TXH_OperatingInstructions0512.pdf
Blu-Ray Player: Sony Playstation 3. 280W = Minimum UPS 400VA / Recommended UPS 500VA
http://www.us.playstation.com/Support/Manuals/PS3
Continued in Part Two...
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