It shouldn't be "too" expensive to overhaul your PC. I swapped all of my components from the AGP era to PCI Express for just under 300£ (Or thereabouts in local currency). You'll need to get a new Motherboard, CPU, Graphics Adaptor and some RAM at any rate. Perhaps a new PSU as well. It isn't going to be cheap, but it would be FAR more cost effective over a short span of time than to invest in AGP cards at this point.
@Dayve: I have similar specs and I agree. It really looks beautiful.
