How can i make a small speaker system with USB Ports?

What I'm wanting to build is for my father. The idea is i give him a box with a line outm a small lcd display and four USB ports, each with a button to 'select them'. This is so i can give him 4 USB sticks with 'Classical, Jazz, Opera and World' written on them and he can choose what he wants by pushing the select button by the port, which would then channle the main porcessor to search the disk, pull it up on the screena nd then offer the normal push play or stop, next last etc... buttons I am supposing that I can use a cheap USB Flash MP3 Player to be the heart of the system which I'd like to make Main's powered, Anyone got any ideas?