Setting up a poker station

I just boguht a PCIe dual output video card for $50 on newegg.com Mostly everyone here would recommened it for cheap, reliable parts.

[BasketballNYC]

If the computer I have has onboard video, would a dual output card bring that up to three monitors or would I have to disable the onboard entirely thus dropping me to two? Also, how will processor speed effect performance of the tables and added items (GT+ specifically)

Thanks for all the help.