My favorite is the headamp GS-X mk2. Neutral, Transparent, has been able to drive the headphones I have tried with authority. Anyone who has complained that the HD800 is weak in bass should give HD800 being driven by the GS-X mk2 a listen. Just make sure your source is high quality, because if it's not, the amp won't cover it up.
I was waiting for someone to post about the gsx here! i have hard it at a meet and it was awesome! I AM waiting for justin to build the next batch. it should be ready for my birth day!