headroom total airhead was 149(under your budget) and now 99 dollars. from what i read, not worth 149 but 99 is ok
http://www.headphone.com/products/he...al-airhead.php

i'm also looking for a portable headphone amp and have been thinking a chinese amp named c&c box. it's about 99 dollars. you can get it from e-bay or here
http://www.head-fi.org/forums/showthread.php?t=220470

it has an review and where you can get it