Just to let you know what is possible.
I am running 4 monitors on Win XP Pro with a G550 agp dual card and a G450 pci dual card in the same computer and it works flawlessly.
Before I got the G450 I was running the G550 agp card with two Diamond Viper 330 8mb pci cards in a Windows 98 machine.
The only problem I had in the Win98 machine is that one of my monitors operated at a lower refresh rate than the other three. When I would reboot all the monitors would be reset to that lower rate and I would have to manually go to the display settings and reset the other 3 to the higher refresh rate.
I have now upgraded my 4th monitor when I got the new computer and don't have that problem because they all operate at 85hz.
I am running 4 monitors on Win XP Pro with a G550 agp dual card and a G450 pci dual card in the same computer and it works flawlessly.
Before I got the G450 I was running the G550 agp card with two Diamond Viper 330 8mb pci cards in a Windows 98 machine.
The only problem I had in the Win98 machine is that one of my monitors operated at a lower refresh rate than the other three. When I would reboot all the monitors would be reset to that lower rate and I would have to manually go to the display settings and reset the other 3 to the higher refresh rate.
I have now upgraded my 4th monitor when I got the new computer and don't have that problem because they all operate at 85hz.