I was thinking of picking up a relatively cheap AGP video card to upgrade from my Radeon 9800 AiW Pro and my eyes fell upon a BFG OC 6600GT for about $170 CAD. Will there be a substantial increase in performance if I picked one up?
Don't do it. The cost/benefit is too high. The 6600GT is a little better, but not enough to invest that much. Get an X800 or X850 series card if you want an upgrade. Or just wait and get a higher end PCI-E card if you upgrade motherboard and processor down the road.