You might be surprised by what you can get away with driving those from. I am amazed by how decently my MDs do with my HD580 without additional amping, even the N707 with only 5mw of power can push it well enough to sound good, even if it can't take them to their full potential. Since those Senns are fairly sensitive for their high impedance, they can reach a reasonable volume straight out of a portable unit, though the volume will probably have to be just about maxed out. A great pair of headphones, I'm sure you'll enjoy them. fighting words...