I'd like to get my 13 yo son this app but am concerned about the system requirements and performance. He'll be running in on his G4 tower but it's an older Sawtooth (400 mHz, 576 MB RAM). I've updated the graphics (Radeon 8500) and am thinking of throwing in a processor upgrade. Does GB run well with these upgrades (am thinking of bumping it up to 1.5 gHz OWC)? Any thoughts on USB keyboards that'd be appropriate? He plays piano and drums and is in his school jazz band.