I would look at Woo and Decware. They may be a little above your budget but resale value is very good on headphone amps and many have preamp outs. You might also pose this question on Head-fi, where headphone junkies hang out discussing the latest and greatest giant killers in the world of headphone amps. I am sure they will recommend something within your budget.
good headphone amp/preamp?
OK, looking to get a headphone amp for Senn HD 600s that might also do duty as a preamp running with my ATI 1502 or Mcintosh 250 and Ohm Walsh 2s given some space issues? I saw writeups on a couple of ideas in Stereophile...Little Dot, Music Hall...Chinese tubes for small $. Also, have seen things on the 'gon, like Canary. Looking for something under $500...$300 might be better. Any input is appreciated as I will be bying off the net as I wont find it out here in HI. If it is only good as a headhpone amp thats ok too as thats my primary need. I listen to lots of jazz, acoustic, female vocals,guitar and piano, 70s singer songwriters.