Headphone amp for Sennheiser HD 600/650?


What are the most synergistic headphone amps for use with either the HD 600 or 650?
128x128zavato
IME the Schiit Asgard headphone amplifier matched well with the Sennheiser HD600s when I had them.
I am using a Woo Audio WA6SE with my hd 600s and 650s. I am also using Stefan Audio Arts and Cardas cables with these phones. Great match, imo.
No doubt the Woo's are wonderful, but at a price, of course. I've found great synergy with my HD600's in a Peter Millet Mini-Max, which (if you are into DIY) can be built as a kit for about $260. Or purchased used or from various builders over at head-fi.net