Which AWS EC2 instance type is most optimal for audio streaming?

I'm in testing stage of launching an online radio. I'm using AWS CloudFormation stack with Adobe Media Server.

My existing instance type is m1.large and my Flash Media Live Encoder is streaming mp3 at 128kbps which i think is pretty normal but it's producing a stream that isn't smooth & stable at all and seems to have a lot of breaks.

Should i pick an instance type with higher specs? I'm running my test directly off of LiveHLSManifest link that opens on my iPhone's Safari and plays on browser's build-in player..which doesn't set any buffering on client side - could this be the issue?