Yamaha YHT-397BL or Denon DHT-591BA?

I have the Yamaha 395 and have been quite happy with it. The speakers are ok for our size room but definitely an upgrade should be considered down the road. We've had it for over a year now and it has played extremely well with the other components. YPAO calibration is a bit more cumbersome but you can achieve very good results with it. Audyssey is more automated and is supposed to give you better results but personally I'm not all that convinced. If you are a real audiophile it might be the way to go but it all depends on room furnishings, if you always sit dead center, etc. Denon makes good system and BA speakers are fine as well. You might want to look at the sensitivity of the speakers for comparison. My Yamaha's aren't as sensitive as I'd like (Yamaha isn't known for their speakers) so that's why I'm looking around, but blu-rays with lossless audio sound really good with what I have now.

My room is about 17x20, with an 8' cathedral ceiling. Big sliding glass door on the left side of the HTS (curtain covering), carpeted floor, and leather furniture. Fronts are at least 6' apart and the sides are even with the back of the couch (which is against the wall). Speakers are set to small and the crossover is set at 80Hz. Subwoofer volume is set at about mid-point. YPAO calibrated. We don't listen to window-shattering volumes so that may be a consideration if you do. Seating is whatever is comfortable for whoever is there ( I usually sit dead center when watching tv/movies but not always). I'm not sure about 4k passthru but it sounds like a spec that is available once 4k is offered (if ever). It seem that a lot of mfrs will claim specs that aren't yet consumer-ready, at least that's my read. I don't worry about those specs. The Yamaha matches well with my LG LD520, Panasonic BDT-210 BD player, and the AppleTV2. TV is calibrated so I don't use any of the artificial video processing available on the Yamaha and the Panasonic. I also don't use any of the artificial audio processing that is available on the Yamaha (which is actually the RX-V371 receiver) AVR. I play the audio as recorded, whether it be BD, DVD, or OTA tv.