Yes! With Mega Song Storage, your music will also stream at whatever bitrate you have uploaded it at. For example, without the service, no matter the bitrate of the file uploaded, the player streams the file at a bitrate of 128.
With the premium service, if you upload an mp3 with a 192 or 320 bitrate, then the song will stream at that rate in the player! (Note: Even without Mega Song Storage, if the song is available for free download, your fan will always receive the download at the quality at which the file was uploaded). Mega Song Storage also allows you to overwrite current song files and replace them with newer mixes or versions.