I definitely think you should get as much ram as you're willing to also, but I should point out that it will not fix the eBay issue. There's some coding issue between eBay and Safari. At least on my computer (iBook G4/800/640MB), I get significant beach-balling on eBay in Safari, and none in Firefox. There was another thread about this recently, and I don't believe anyone reached any conclusion of a fix for Safari....
I had been using Firefox, but I've been getting some weird system crashes recently. Once or twice, the system completely locked up, including full mouse and keyboard non-responsiveness, with no KP screen or anything, forcing me to reboot. I'm trying to root out what might be causing it, so I'm back to Safari temporarily, because I only got these after going to FF. Hopefully it's something else though, because I'm starting to miss FF.... 🙁