suggestions for a headphone amplifier

I recently bought a pair of Senn 650s. Up till now I have listened through the headphone jack on my Jolida JD100 player. Well, that only gets you so it's time to liven it up with an amplifier designed to make the most of whatever these 650s have to offer. I am ready to choose based on the groups suggestions, so show me what you've got!
Another vote for the Antique Sound Labs Head MK III. This is a fine, economical intro to the magic of the SET experience. I thought the MF X-Can perfectly capable, but the ASL added that special quality of living air; with a marvelous hang-time for a note's resonant fade-out ...
It's one day later and I am savoring all of the suggestions.Some additional snooping on my own has uncovered Audio Valve RKV MK11, Singlepower offerings, enen a Gillmore new offering or the established Little w/ dedicated power supply. In some instances my 500.00 dollar ceiling is blasted, though I knew that would occur anyway. Headroom amps are for the most part unavailable for now, and I guess that their new line won't show for a month or two. Looks like there's a ton of great product out there. Tough choices!!!!!!
Don't forget to replace the stock 650 cord with the Zu Mobius one. I use a Headroom Max amp (with the new reference module that is in the latest version). This all works fine with me. Kubala Sosna Emotion ICs work well well with the 650s, as the ICs complement the 650's slightly dark sound.
There are several aftermarket cords for the Senn 650s. I like the Equinox cable. Others like the Zu but some say it's too bright. I tend to prefer a darker presentation.