I have a 500MHz G4 tower. 100MHz bus speed, and doesn't support Duals. I have it configured with 2GB (4x512) of PC133 RAM and a 32MB nVidia GeForce card that supports quartz extreme. Ideally I'd like to add a card with core image, but that's a bit pricey for the moment. I'll be adding a PCI ATA controller card soon to help my disk performance. However, the one thing still completely limiting the computer I think is the CPU. I've been research upgrades, and I think I have it narrowed down to a couple, and I'd hoped someone would have an opinion... 1) 1GHz Sonnet SG4-1800 with 2MB L3 cache...about $170 2) PowerLogix PowerForce47 1.4GHz CPU, no L3 cache...$170 3) GigaDesigns 7A-1800U 1.8GHz, no L3 Cache...about $230 4) Sonnet SG4-1600 1.6GHz, no L3 cache...about $215 Those are my main targets...if you have other suggestions I'd love to hear them. Either way, your advice would be invaluable. I want a quick machine, but I have a MBP Core 2 Duo as my main every day machine. This will be used mostly for lighter work, but I need it to feel nimble and responsive (the ATA controller should help this too, right?).