I have been using two very different video cards on my Gigabyte X58A-UD3R board (4 PCI-E slots)
1) NVIDIA GTX 650 driving two biggish monitors, and that I use for occasional gaming.
2) Radeon 2400 PCI (not PCI-E)in the single PCI slot, driving two smaller monitors, used purely for low power stuff, like word processing, etc.
This has worked great up until now, but the old Radeon PCI card has just died.

My question.
PCI (not PCI-E) cards are increasingly difficult to find. Therefore, can I put another cheapy PCI-E card in one of the remaining 3 PCI-E slots? It doesn't need to be at all powerful - slow and fanless would be great.
Would this need to be NVIDIA like my GTX 650 becaus of driver issues, or could I put whatever I can find cheaply in there instead?

I'm not interested in SLI for gaming, and I need the four monitors for work, but only two of these need to be at all quick.

Thanks for any ideas.