You've made some interesting suggestions. As for my Creek, I'm not very dissatisfied with it, I've heard its a pretty basic, lower-end amp and wanted to try something a bit better. I didn't buy the Creek for the HD650s, it was just an amp I could afford at the time. What would you recommend as a good pairing for HD650s? As for the Denon receiver headphone jack, it isn't bad for a built-in unit, I just thought I would get more (in terms of power, control, and sound quality) out of a dedicated unit (after all, I doubt Denon put several hundred dollars of technology into the headphone jack, which is usually an afterthought on receiver units like this. That said, I really like Denon...). As far as what I want out of the sound, to be honest, I couldn't tell you, I've never tried any other amps. My ignorance in this area is driving my exploration, I just need a bit of guidance to see what I may be missing. Thanks!