Category: 
If 8 is enough.
Matrox M9188 PCIe x16
Drive Multi-Display Monitoring Environments with Feature-Rich Octal Graphics Card
Other configurations / arrangements are selectable via software settings.
Max DisplayPort Resolution per Output: 2560×1600
Max DVI Resolution per Output: 1920×1200
Pretty cool – and Spendy, too! $1.995(?), plus monitors.
When you get that up and running I may have to buy another gun just to have an excuse to come over and check it out.