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.