If you're running Leopard with no issues and all your doing is using iTunes and an external drive, you should be fine.
I was using an iMac G3/450 with an external 500 gig drive, running 10.4 and it worked fine. I have since upgraded to a Mac Mini.
I was using an iMac G3/450 with an external 500 gig drive, running 10.4 and it worked fine. I have since upgraded to a Mac Mini.