I'm looking for an amp/DAC combo, or just a separate amp & a DAC, to use with the Denon AH-D2000 and the Sennheiser HD650 headphones. I do not care about portability, aesthetics or anything else that doesn't affect sound quality & performance. I'm just looking for the best sounding and best performing amp & DAC (costing a total of) around $500 or less. (Straying slightly from that budget is fine.) I also have no preference regarding tube v. solid state designs. I've been reading many reviews, forums & topics, consulting with different manufacturers, etc...
I have yet to find any clear discussions on what sounds best with both low impedance & relatively high impedance full-size cans within this price range, regardless of portability, design & aesthetics. (I realize & understand how subjective "sounds best" is, which is why this is intended to be an opinion-based thread where individual opinions are respected. Most audio-related topics are ultimately subjective.) I think this is a worthy topic that deserves a lively discussion.
So, keeping all of that in mind... What do you think? What are your favorites?