I've been running a 4311 in my HT SS8 based set up for about a year with an AVA 600r driving the mains, and an aux amp driving the rears In that usage (7.2) the Denon is actually pretty strong, and significantly better than most of the mass market units in build quality. It has taken me quite a while to get things dialed in, and I'm still working out the specifics on acoustic treatment. Sound with a good recording in two channel is excellent (for the money). The separate amp is a big step up in performance.
That said, I have run the same speakers with my trusty dedicated two channel pre-amp, and for pure two channel listening it wins. When I hook in my active crossover and use the sub, even better. At some point I'll pick up a pre with HT bypass which should give me abilities for both multi and two channel relatively easily. The built in features on the more recent HT units shouldn't be discounted for that use.
My suggestion is build out based on budget and your own listening preferences. You can always add on/swap out as time and funds permit (I'm having Jim build another sub to clear out some nulls in the room).
-- Ben