I pretty much concur along lines of Rlwainwright. Separates, yes, would be strongest sounding/performing option, sonics wise. Better amplifier with separates, like 95% of the time, by default - weak amps in ESPECIALLY lower priced AVR's. If not, then get the AVR and consider adding an outboard amp to that mix with AVR that has Pre-out's. If you can't - or don't want to - go with multiple boxes, and stay AV receiver all-in-one, then I suggest the most features, DEFINITELY WITH A ROOM EQ, 4K pass, 3D, switching, Bluetooth, connectivity, whatever, you can find in an AVR. Used market and refurb (warranty?) gets you MUCH more bang for buck, as this stuff depreciates down to $0.10c on the dollar from MSRP like nobody's business!! Believe it! Buy new, and you'll get less, weaker amps, and less power for your dollar (although lots of features for money these days, regardless, minus preout's) .
That all said, either way, I'd strongly recommend a warmer sounding receiver (crossed over to 100-80hz to a sub) and or amplifier in the mix, to balance the slightly cool somewhat analytical yet clear sonic character of Deftech's, such as Denon, NAD, Onkyo, Integra, Sherwood, and such for AVR's. For amplifiers, consider used Parasound, Classe, NAD, Integra, Sony ES, Outlaw(?), Bryston, etc, and similar, with warmer more forgiving tonality.
Million choices and directions. I'd prob steer away from Yamaha, Pioneer, cheaper Marantz, and even the otherwise superb HK's with your Deftech's, if I had to guess. Anthem?..might be tick bright, but then maybe not. Otherwise top tier AVR with EQ and refinement.
That's my experience of playing with this stuff for decades now. Some pieces may vary of course.
I'd recommend the