Which UPS to get depends on exactly what you plan on plugging into it. For instance, a 667MHz Intel Celeron system with a CD-ROM, integrated graphics, etc running off a 200W PSU will consume a lot less power than a desktop with a Intel Core Duo, 2 DVD burners, an ATI Radeon X1900 XT graphics card, etc running off a 600W PSU. Same goes when comparing a 15" CRT to a 19" CRT.
My suggestion would be to click here and use the APC UPS selector to help determine what's best for your setup. You don't have to purchase an APC UPS (Belkin is another good option, though I prefer APC for price and quality), but it will give you an idea of what to look for.
Something to keep in mind is that you also need to protect your phone line, coaxial cable line, etc since a surge can enter from any point, not just the power cable.
In regards to plugging a surge protector into a UPS, it's not recommended. It does not really provide you with any additional protection, it provides the potential to overload the UPS, it can cause grounding issues, and it may void the warranty on the UPS and/or surge protector so that if it doesn't work properly and you lose everything you are entitled to nothing. In short, I wouldn't do it.
Hope this helps,
I was wondering what power level UPS system I should get. I am running a desktop pc, monitor, dvd writer, and powered speakers. I also use a laser printer but that does not run all the time. Also what would happen if I plugged a Surge Protector into the UPS power box. Would it cause damage? Thanks