The M80s are wonderful. Rather than getting an amp for it, though, you might want to consider getting a better digital player. The Samsung Galaxy S2 is renowned for having very poor sound quality (I had it myself, so I speak from experience - it really is very bad). The Samsung Galaxy S3 sounds much, much better, but you don't have to upgrade your phone - something as cheap as a Sansa Clip would be a considerable sonic upgrade for you.

Glad you like them, I find them to be very capable portable headphones aswell. As far as an AMP goes, there is no real need for one with the M80, you won't really note a difference. Depending on your soundcard you might want to invest into a DAC, so you might want to read through this thread (among others) http://www.head-fi.org/t/623840/best-amp-dac-for-v-moda-m80s