Thats what I would suggest. I learned my mistake years ago on proprietary surround HTiB's like Sony and Panasonic have offered. These Denon's, as well as Onkyo's that give you a REAL rcvr, are the best, because you can upgrade it over time. Get the best one you can get now, enjoy it, and add speakers as you can. The 591 is 3D capable and 1.4, so it's in for the long haul.
Id say your entire plan is pretty good. I went from a HTiB to Onkyo 605 and some Polks. Bought a Denon and then some Def Tech's, never looked back.