PCIe x16 and PCIe x1 cards

I want to use three monitors with my HP machine.
I got to konw from this article that I need to have two similar vendors cards in order to achieve that in Vista.

I only have 1 x16 slot
Now I have a Nvidia GeForce 8400 GS in my PCIe x16
I was wondering if anyone can suggest which video card will be compatible as well as a good choice for PCIe x1 slot.

Thank you

There was a thread about this somewhere on the forum - it was pretty useful IIRC. Let me know if you can’t search it up. I think it was in the General CUDa forum.