SerzThis is a pretty good dac/amp, not sure if it's the best at this price though. I thought it would work well with low resistance dark sounding headphones. I don't have a fostex headphone but going by the reviews of TH-X00, this dac/amp *might* be a little too bright. YMMV
SerzI use a modded Matrix m-stage hpa-3u+ I bought from massdrop with my (bright) HE560. Stock matrix's dac sucked big time. The combo is pretty sweet. If you're thinking about spending big $$, may be you can buy a used Gumby + the hpa-3b (balanced version) and give it a spin and have much better setup.