I buy this amp to power a set of akg k240 mkius 's and some Grado SR60i 's from my Zune HD mp3 player . it be great . the grado 's take less power than the AKG 's , so they be a little louder , perfect actually , because I 'll find myself have about 3 notch leave to adjust a little higher on song record quieter . I have yet to try the AKG 's with the amp , but do not expect anything amazing because they be pull a 55ohm load for they volume , and that be alot . as far as feature go , it be full of they . it have a bass boost switch which I always keep on because I truly think they then sound fuller , and the rechargable battery be a great thing because I can come home and charge the amp right alongside my Zune and Cell Phone and everything will be ready in the morning . thanks Fiio for a grrreat product ! well worth the money .