Well TobyDZ, With a slower CPU, AGP's are usually a little faster then a PCI-E is due to AGP's have DMA. Why don't you visit my website and look over both versions of the 850 PCI-E vs. 3850 AGP. You will have the proven facts that you need.
www.agpbattleground.com
Please note, I need to make a little update on my website informing the readers that the VIA chipset is usually the slowest chipset.