Greetings from the Land Down Under :-D
I'm running Jag (10.2.5) on my iBook 500mhz and it works great. Just a few things to be aware of though, make sure you max out the Ram and HD. Also be aware that Quartz extreme runs on a G4, so maybe look at the 12" PowerBook if the budget allows.
The upside of buying a Mac is that it should still be working after 10 or more years!!!! I also have a Duo 230, and although it is only running system 8.5, it is also running Office 98, not bad for a 10yo laptop!