I have leopard running on a 1.25GHz eMac with 512MB of memory. You'll be fine with 1.25GB. 1-2GB of RAM for leopard is over kill. I mean, it's nice, but definitely not necessary. Safari 4 opens on that eMac in 1 bounce. I couldn't believe it when I saw it. If you want to be running a ton of apps simultaneously, then I'd consider upping your RAM, but with 1.25GB you should be able to do a lot more than my fiancee does on the eMac and she can run probably 3 or 4 apps simultaneously (nothing too intense, of course).