I have not heard them side by side. It is my perception that the Denon is not as warm as the HK. But this is up to debate, some say that receivers, and more so amps, do not sound different. I think I have heard differences

I used to have a Marantz SR4300, and when I switched to the HK 525, there was a noticeable difference in my 170's at the time. More clearity and detail. Of course there is also a difference of almost three times the retail price as well.

No up conversion on the 525.

I am looking to get a multichannel amp, and use my 525 as a pre/pro, then eventually get a dedicated pre/pro.

-curtis