The Headroom company specializes in headphone amps, including ones you can carry around with your iPod. The Total Airhead or Total Bithead models might be what you need. I gave one to one of my sons and it is really not bad.
http://www.headphone.com/
Headroom's portable amps
There are other small, battery-powered headphone amps available also. You may find a few names to look for if you visit head-fi.org.
http://www.headphone.com/
Headroom's portable amps
There are other small, battery-powered headphone amps available also. You may find a few names to look for if you visit head-fi.org.