I think that +One PC card would be the one you are looking for. They have got ADs in the Digit Classifieds section.....don't know if its that good though. I think the Card itself costs around 6000 bucks....
well if u just need 2 Monitors on one PC then u will need a graphics card which support Dual Monitors ....but if u want 2 monitors to do 2 diff works ..then +One PC is one of the solutions ..+one connects to ur PC+Keyboard+Mouse etc..so that u can simeltaniously do 2 diff jobs on single PC ...