I used HD580 (same drivers) with Benchmark DAC1. More money but great sound. It can also serve as a preamp or portable unit for travel with laptop.
Sennheiser HD650 Headphone Amp
I have unexpectedly ended up with a HD650, and do not have a single component with a headphone jack, though it sounds surprisingly good direct into an ipod. I would like to find a headphone amp, under $200 used, or possibly an integrated amp or CD player with a good headphone jack. I liked it plugged into s friend's Decco but would prefer not to spend that much.