I have to fess up that I have been using two Denons receivers for several years. I also like their disk players quite well.
I don't understand why you might consider a center channel a must addition in the future. Good, old fashioned two channel sound has been lusted after for about three generations & still has its followers who want to maximize their speaker budget by sticking to the best two for the front L&R that they can afford.
The purpose of a center channel is to firmly anchor the dialog close by the screen in a surround sound setup. That situation then substantially demotes the importance & use of the front L&R, which you tried to buy your best at that stage of the game. A center channel typically is getting, oh, 65% of all the audio energy. It goes back to the original, monaural speaker sound coming from the movie theater screen for normal dialog direction. A step of introducing a center channel would be, perhaps unwittingly, a move to then embracing a surround setup.
I hold no affiliation to my nearest big box store, like BB, because 48 or however months no interest is not how a form my decisions as to what A/V equipment to purchase. The long term satisfaction quality of the desired experience, is.
To logically move beyond that is the natural progression to consider the speakers the most important part of the scheme. That is where most all the practical level sound difference comes from. Receivers have become much better than the old days & excellent values to boot. They get the advertising focus as they have annual model changes. They are made with a goal to not color the sound reproduction &, for the most part, they have succeeded.
Buyers tend to perhaps overbuy their receiver needs. Others may disagree with me, but I don't regard a need for, say, more than 100 watts per channel to be necessary. Many factors come into play, of course, including efficiency level of the speakers & speakers whose impedance falls to low levels rather than a typical 8 ohm level create difficult loads which may require more sophisticated power source.
Yes, early rock 'n roll was my enthusiastic source of hearing loss. Nowadays I only find those who somehow feel an obligation to broadcast to the neighborhood, annoying. The volume knob on my receiver never goes beyond half way. And that ain't parlor music, dude. I have fairly wide musical tastes.
So I present the proposition you cannot buy a pig in a poke, but get out to give a serious listen to possible speaker selections. No speaker is perfect & each brand has their own sound character. It is worth a quest to find which, within your budget, will be overall most satisfying in the long run. Speaker cost may seem high up front, but they don't just easily wear out, but give pleasure or many years. A bit of confusion is normal, but it's worthwhile to decide which seems best to your own ears, no one else.
I shop for information & price levels online, but want to see if I can deal with experienced, independent A/V dealers. They have already survived the invasion of the big boxes. They are generally more knowledgeable than personnel in the big boxes. They don't attempt to carry dozens of brands on the shelves, but probably have something which is a good match for you. There are occasional very snooty stores, but most of these, who carry somewhat higher end goods, are very happy to assist a small budget customer who might be an even better customer in the future.
Weren't the mom & pop store posts in another thread? Fine that you are really deeply into guitar, but that is not the thread topic. You could do some fast remedial speaker education with an article from the Feb 2008 free, online mag, Playback. It'd actual topic is bookshelf speakers under $1K. I won't get into whether bookshelf size speakers can create a nicely, quite loud sound.
Check out the article @: http;//magazine.playbackmag.net/playback/200802/?u1=texterity
No list can be all knowing or comprehensive, but this one is a nice as I've seen. Survey what brands may be accessible in your area, then get out to hear some seriously. Take at least one CD which you are intimately familiar with & that has substantial vocals. Vocals are mid-range frequencies, but are surprisingly difficult to reproduce well. That is before even considering bass or treble.
Trust your instincts. If you think you may have just heard distortion, you have. Take simple notes as confusion comes oh so easily. Maximize the proportion of budget for those most important speakers which seem more overall pleasing to your ears, & your only. In contrast to you, my "snooty" gear is my sound equipment; a guilty vice.
For a possible real find in huge value speakers, if in California, where they are made, Ascend speakers may be a value benchmark. Hear them if you get a chance.
Keep in mind the goal here is your pleasurable experience. Enjoy.