Hello i have a pair of audio technica ATH-M50 and was wondering what a good portable amp under $100 would be ? I have a samsung galxy s3 dont know if that matters. I was looking at the fiio e11 is that any good? And Will the M50s benefit from an amp?

The E11 is very good for the money, one of the best. See how it compares here and make your choice based on what you like: http://www.head-fi.org/t/596482/the-sub-100-portable-amps-shootout-11-1-amps-compared

Rankings of the different amps follow the reviews.

The M50s will benefit some from an amp. Probably depends more on what volume you listen to them at. If you are close to max volume or like to use EQ boost at higher levels, then an amp will give you better dynamics and let you play it louder. I personally don't use an amp with my M50s with my Samsung Note 2 or Sansa Clip+ because I don't need the extra volume and the little bit of difference in SQ just isn't worth it to me.

One advantage of the E11 is the bass boost if that's what you are looking for. That can be a plus if you are a basshead

Do you ever use them with your computer? If you don't have a good soundcard with it, then an Audioquest Dragonfly or FiiO E17 could be a nice upgrade. Both of these are DACs + headphone amp. The Dragonfly is for computer use only. But the E17 can be used as a portable headphone amp with your S3 and is generally considered comparable in SQ to the E11s headphone amp.

You really try to save money for a Fiio E12, or just buy a used unit.
it is really an upgrade from the E11's... it'l provide you with better SQ (in all areas).

@Cel4145 thanks I appreciate the help. I'm definitely a basshead at times I love details in music and sometimes I want a ton of bass. so I will definitely use the bass boost. And as of now I don't have a computer but iam gonna buy a nice one very soon so I will definitely look into the e17 and the e12 thank you both for the help!

Then check out the sub $200 amp shootout as well. The E12 is reviewed in there with the rankings: http://www.head-fi.org/t/620775/the-sub-200-portable-amps-shootout-13-11-amps-compared