No - see the first two posts - you already have a preamp in your receiver. Bignerd did a good job of describing the combinations and permutations of receivers, amps, etc.
The preamp is where the signal goes in on your receiver, and the manipulation of the signal happens - tone controls, balance etc. That output is then fed to the amplifier.
What I'm trying to say is to turn up the signal from the MP3 player to the point just before distorting (if it does distort - it may not). Use the loudest signal from the MP3 to feed through the preamp and into the amp.
The reason for this is that you then have the loudest signal possible going into the preamp which means that you amplify the maximum amount of signal, and minimum amount of noise.
Good luck.