Here is an interesting experiment from the Harmonic 313 Laboratories. Mark Pritchard took one bar of his track Word Problems and sequenced a track consisting of loops from the original master and MP3s at different encoding rates.
The purpose is to demostrate the loss of quality when encoding a file using lossy data compression. Unfortunately, there is no more data like which encoder was used and what kind of settings have been chosen.
While I find this experiment interesting and look forward to more of this, there is also a valid argumentum e contrario: MP3s might just be enough for you, depending on your ears and audio-setup. Anyway, you can download Test No. 1 and try it for yourself.