This is a 600MHz iBook G3, right? It should support Tiger -- you can probably buy a copy for about $20-30 USD... otherwise, iTunes 7.7 runs on Panther...
I'd had iTunes 4.7.1 installed; and I just installed 7.7.1. Couldn't have been easier, and it works fine.
And the runner-up is still available: Audion, from Panic Software. (For free, of course!)