There are a lot of cases in receivers/pre-pros where a higher price does not lead to any actualy improvements in sound.
One thing that DOES make a difference though is Audyssey MultEQ XT32. This highest-level version (other than Audyssey PRO) of Audyssey's auto-setup/EQ is substantially more sophisticated and capable than any other auto-EQ program that is out there right now. When you are playing in this $2500-ish price range, MultEQ XT32 is a must have feature, IMO.
To that end, out of your short-list of candidates, the Denon AVR-4311CI or the soon upcoming AVR-4312CI would be my top recommendation. If you discover that you require or would simply like more power from a separate amp, you always have the option to add separate amps with the 4311/4312's pre-outs.
There are the options from Onkyo as well. Their entire TX-NR5008, TX-NR3008 and upcoming x009 receivers and the PR-SC5508 pre-pro. Other than the THX processing though, the Onkyo's have nothing else to offer over the Denon. The upcoming TX-NRx009 Onkyo receivers will be worth consideration though due to their more capable Marvell Qdeo video processing.
In any case, keep a look out for MultEQ XT32 because it is a very worthwhile feature, IMO.