[Hesky]

Rega EAR is a great little headphone amp, they pop up on ebay once in a while, I can also highly recommend the Musical Fidelity X-Can headphone amps.

If your pretty handy with a soldering iron there are some pretty awesome DIY headphone amp projects out there, both solid state and tube based. I made a Pass Labs based Mini Zen headphone amp with my friend a while back. It was based around a single gain stage class A topology and cost just £50 in components to build, the sound it produced was superb!! better than any dedicated headphone amp I had heard up until then and just me and my buddy made it. I want to built another one but with more exotic capacitors and pop it in a cooler looking enclosure.