looking for portable amp for Sennheiser HD 595s

Hi all,

Looking for a spot of advice. I have just bought a pair of Sennheiser HD 595s for my iRiver 340 on the way to and from work (high quality oggs), and for using on my home/work computer for listening to CDs and again high quality oggs.

Happy with the sound quality from the Senns so far but I hear that this can be improved on greatly with a decent headphone amp. Amp must be portable so looking for a battery charged option and not looking to spend a great deal (~£100 at most).

Pretty new to this game. Any advice most welcome.

cheers,
Chris