PCI Graphics Card to Compliment AGP Card

I have a QuickSilver dual 800 MHz G4 PowerMac with an nVidia GeForce 2 TwinView in the AGP slot. My Mac is used for video editing and the AGP card provides output for two displays. These days I wish I had a third and fourth display so I am thinking about buying a PCI graphics card to work along-side the card I have allready.

The only Mac PCI cards that I can find are made by ATI and I am worried about compatibility between that and the nVidia card I use. Does ATI play nice with nVidia?

I have also heard that Mac PCI graphics cards are intended for 66 MHz PCI slots, which is what the B & W G3 PowerMacs used before Apple adopted AGP. I am not even sure what speed my PowerMac's PCI slots run at and if they would be compatible with a card intended for 66 MHz PCI.

The PCI card I want to purchase should have dual output with VGA and S-Video. The reason I need to output video through a graphics card to a television monitor is that Final Cut Pro 3 struggles when streaming Off-Line quality video through a DV converter.

One of the four PCI slots on my PowerMac is used by an UltraTek 100 ATA card and I hope performance does not get degraded because of this.

If anyone reading this has real-world experience with such a set-up please share with me what the best option would be.