4 Monitors with windows 7 combining pci and pcie ?

Hey gang, sorry for the noob question.

I am not much of a hardware guy and googling gets you millions of opinions, all from strangers and some of whom may work for certain interests and slag a competitor's product.

I've heard you guys are the authority.

Anyhow, here's the deal

Windows 7
asus a8n-vm
Nvidia 8500ge force
athlon socket 939 2.2 ghz
600 w power supply
4 mb ddr ram
2 x 250 ide hds, 2 x 1 tb extrnals

At this exact moment in time, I have two monitors, both plugged into the geforce which is using the lone pcie slot. They are setup as their own display (not sure if that's the right word, but the display is not repeated; i drag apps, docs etc to the second monitor and use the primary for other things). One uses the vga, the other uses the hdmi of the video card.

Mobo onboard vga unused

I just bought a soundcard which will use one of my 2 pci slots.

I was strongly thinking of buying 2 more monitors and going with a 4 monitor setup.

Ultimately what I want to know is:

1. does windows 7 allow it ? for what I have been reading it will allow up to 10.

2. If I have one video card in the pcie slot, can I use a pci video card for the second pci slot (first pci used by soundcard) or will the video card in the pcie slot "cancel out" the second video card in the pci slot ?

If possible with another pci card, is there any particular "spec" of card i should/would need ?

Thanks in advance to all who help !!!!