You really need a G4 for OS X to feel enjoyable and speedy, even if you are only web browsing or whatever. And you'd be best with Leopard, because its the most secure and software will be supported on Leopard for at least another 2 years. This is not the case with Tiger and any prior versions, which are no longer the focus of software developers. By all means get a Beige G3 or iMac G3, but OS 9 is really the best OS for those machines.