Interesting..After reading the review on this over at Audiosciencereview, I think I might get this over the monolith THX amp. Really itching to get a fully balanced set up going. Has anyone used this amp with the HD650/660s?

Haven't used this amp with those headphones (I have the HD 650, and 660s), but looking at the specs..should work fine with either of those headphones. they both have relatively low impedeance, so this amp should deliver more than enough power.

I have been powering my HD 800 with an Asgard 2 w/ Bifrost Uber for the past year. To my ears everything sounds very clear, there is absolutely no floor noise or distortion even with the volume cranked. Although you will probably need to EQ the lower end to be more pronounced.