I am running Carrara V2.1 on an 8600 with a G3/400 upgrade card. It's fine. The cards are very reasonable now. You can get a Sonnet G4 /800 for $400. It really depends if you are expecting to keep your old warhorse for a few more years...those iMacs are less than a grand and give you a whole new computer, hard drive space, video card etc.