KVR is Kingston Value RAM, which wasnt Apple tested or Apple Certified. You can buy and test it out on your mac. It will work most of the time, but, do prepare for some Kernal Panic time to time.

KTA are Kingstone Tested Apple RAM, meaning the RAM are "tested" to be work on Mac. If they dont, you have the rights to return for another peice till it works on your Mac. Also that's why it cost more.

Regarding the AGP, both PC and Mac uses the same card physically. But the BIOS/ Filmware are different. You should look for those agp that's specifically made for Mac. There's also ppl that flash the PC card firmware to work on Mac.

Any Kingstone RAM dealer can order for you if they dont have it in store.
Price might be 20-50% more than KVR.

Shoot me your quotation for a Powermac G5 dual 2.0

if the G5 price is tempting enough, i dont mind lar.