I haven't heard the Yamaha and stopped considering it when I was looking for an integrated or preamp because it doesn't have all of the inputs and outputs I wanted (I have always had integrated amps with pre-out, MC/MM, the ability to drive difficult loads without flipping a switch and usually, more power). However, since you included the Halo series, thought I would comment. I also never used the Denon for more than 2 channels because my room doesn't lend itself to surround and I hate tiny, little speakers. If I ever do a full-blown surround system, it will be just that- full-blown, with all speakers being the same so the voicing will match.
I went from a Denon AVR-2313CI to the Parasound P5/A23 and the difference in sound is drastic, but I'm not sure it's as much from the power amp as it is from the preamp but I know the Parasound provides a lot more impact and sense of space. If the Denon had Front pre-out, I may have just bought a power amp and been done but I had decided that I wanted to listen to my vinyl again without adding another little box for MC input gain/impedance requirements and the Parasound has a nice phono preamp. At some point, I may connect the Denon's Zone 2 pre out to the Halo amp to find out if it sounds as good as it does now.
I know the Denon wasn't top of the line, but it did list at $999, so it had better be decent, for that price.
If the distributors would let dealers hear the equipment for themselves, it would be easier to comment about the sound but I don't like having to buy something without hearing it. Too much like "Eat this- does it taste like it spoiled?".
One thing I have always like about Yamaha's integrated amps and receivers is the variable loudness contour- they're the only ones who have made it possible to change this to more accurately match our hearing at different SPL.
