JUVS Audio Manager / Format Type for Music

[lowpro3210]

I just got my Mogul up-to-date w/ all the plug ins, apps, and what not. I got the "click here to play music..." on the today screen; my question is what format mp3., wav., midi., etc do you put on it. I know it can pretty much read them all, but I have a TON of cds (.mp3s) on my computer, BUT I do not want to loss all this memory cuz the file sizes are like 4-7megs a song. Is there a certain program I can use to decrease the file size since I do NOT have to have the best sound quality coming outta my Mogul?

Any help is most appreciative & will be given credit...