one thing to keep in mind is that you might be limited by what inputs and outputs the speaker control center has. meaning for example you might get great sound through the integrated blueray player but it might not accept other signals. check this on any device you are interested in before you buy.
you might also want to check out the htib unit from klipsch. i've got the next step up from this set (speakers not sold as a htib) and they sound great. i'm not sure but i think they include a denon receiver and not just some combo blueray/receiver unit found on most htib.
i've seen most of the other htib units... quite frankly the build quality leaves much to be desired. sure they may sound okay but its still just a little plastic box you are spending hundreds on.
for your budget i'd suggest dropping the second subwoofer. getting an extra matching sub is going to cost at least $150-250 estimated. you would be better off with 5.1 now, upgrading the sub in the future to 5.2