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 far....now 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!