g, it's fine buying RAM or a processor on OWC. They're good about those things. But that video card is not only expensive, but it's also a PCI one. It won't go in the AGP slot. Fine for a second monitor, but PCI video cards don't support Quartz Extreme. For the video card, if you want a better one, go to eBay and look for a Radeon 8500. There should be plenty for $60-$80. I also have one, a GeForce 3 that has been flashed from a PC version. It causes a few artifacts on the screen when you first turn on the computer or wake it from sleep, but after that it's fine. I'd let it go for $45 shipped if you're interested.
Also, for the hard drive, buy from NewEgg instead of OWC. They have the exact same drive
here for about $20 cheaper. I'd say to get RAM from NewEgg as well, but NewEgg doesn't stock much PC133, so OWC should be just fine.
You might not even need a new graphics card. It won't help at all for iDVD or anything, it will only really help for making general usage of the OS smoother (Quartz Extreme). Even then, with a 1 GHz processor behind it, it should be good anyway. And with that CPU upgrade, which has L3 cache, it should be about as fast as a brand new eMac, or even faster (with the better hard drive as well).