What headphone amp to use with Sennheiser HD800?

I just bought the new Sennheiser HD800 headphones and I would like feedback from other HD800 owners. Which headphone amps have you used with the HD800's and which they selected and why? I live in a very remote area and I am about 300-400 miles away from the closest high end audio dealer. Your suggestions and comments would greatly be appreciated to help me in choosing a headphone amp for these incredible headphones.