The lowest price on Microcenter is around $50.
If you want to go cheap here's another from newegg
POWERCOLOR RV6P-A3 Radeon 7000 32MB DDR PCI Video Card $43 with shipping
You can get two of these and to suit your needs. If you want to spend a bit more you can get this dual dvi agp card which will give you performance for a few years. The cheaper one's I'm not sure if they're do much video processing, your agp one might do that, if it doesn't then your system might drag a bit. Here's the dual dvi
XFX PVT43KUDF3 Geforce 6600 256MB 128-bit DDR AGP 4X/8X Video Card - $163 with shipping
You said you have open PCI slots, I assume you have an AGP slot thats taken up by your current video card. Looked newegg doesn't have a regular pci card with dual dvi.