Denon or Yamaha

I just dumped my newish Yamaha AVR and replaced it with a separate Anthen process and Anthem 5 channel amp. Sounds way better. Who would have thunk?

I think that's wonderful that the reponders here all like their brands of AV receiver. I'd recommend the Denon, which has historically had a sound that's a match for a wider variety of speaker systems, is forgiving and yet detailed, warm and solid sounding, and has the superior Audyssey EQ system - particularly on up the price ranges.
I also find Denon's stronger, dollar per dollaer, than the yamaha's. At least that's my years experience.
I do like the Yamaha's when mated with an outboard amplififer, often. But Still can't beat the Audyssey processing.
YOu'll have to try something and find out though. I'd start Denon, yes.

This is really not an easy comparison. Each has their strengths.

I've enjoyed both and to be honest would say unless you're looking at the extreme high end of this market, go with whichever offers the feature set you need in your price range.