Yeah, the deal is that the Cheap Denon's with the new Audyssey EQ is going to be LIGHT YEARS better than anything else you could EQ your system with! So, even if you go 2 channel, you'll still be WAY ahead of the game, sound-wise. Infact, you'll be even better off, as you'll be needing less processing power - because you're using only 2 speakers, not multiples, which need EQ'ing.
For you? I'd be looking at high efficiency, possibly horn driver or multiple mid/bass driver speaker designs! You need something that can be driven by lower powered on a budget, if you're not doing separates.
Again, with something like a $450 Denon (retail - much less on net), you should be looking at Klipsch's, Dappolito's, and dual mid/bass designs, which do better at dynamics. That's for bookshelves, and preferably floorstanders, also. For your room, with the Audyssey, you could EQ out floorstandars. But rock will be better running speakers as "small", and letting a powered sub handle the bass! You'll then be bi-amping your system, while getting an active sub into the mix. In fact, I'd be looking at bookshelves, if it where me, and doing a sub, yes. Better flexibility for best sound, all around, I think. However, with an efficient enough speaker, you could get away with EQing it out, and proper setup, for great reasults, if careful. Some speakers out there offer active woofers, so look around.
My first thought for you, for a budget, with superb sonics for you, is the Cheapest Denon with Audyssey, MultEQ. Then look for either some horn speakers, like Klipsch RB-25's, or some Dappolito designs, like Paradigm, NHT, or PSB L/C/R's used on the net. These will all be dynamic for rock, and help reinforce transient response, while being more room acoustic friendly, wiht added efficiency.
Another very strong option for you to look at, in a more high-end, but affordable speaker option, is to look at the Triangle Titus and Comet speakers! These offer a simple crossover, which makes the speaker respond more like an active speaker! This improve dynamics greatly, as does the horn like tweeter they use. These are WELL worth a try for you!
Sub? I'd look at some 10" you find a good deal on, which has a good bunch of reviews. (I found a killer little 8" sub for $20 on craigslist.com). So look around - same for speakers.
You can then scout around for speaker wire cheap, and IC's, tweaks, etc.
Hope this helps.