The 701s need a high quality ($$$) headphone amp to shine. HD580s are a fantastic value and will sound great with the ASL HB1. Additionally - look for a Musical Fidelity X-Cans v2 or V1. Wonderful synergy with the HD580s.
AKG K701
I wasn't sure where to post this so here goes. I'm interested in the AKG K701 heaphones, and had a few questions. Will a Harman Kardon CDR-26 power them ok? I won't be able to afford a headphone pre-amp for a while. If you were going to spend $400.00 on phones which would you suggest? Would I be better off buying say a pair of Sennheiser - HD580 headphones, and a Antique Sound - HB1 Hybrid Tube Headphone Amp to go with it. I can do either one of those options.