Video cards that takes 3 monitors

My motherboard only has one PCIe x16 port, this means I can't plug multiple video cards in it (if I put in the PCI of PCIe port the bios will force me to choose the main one and disable the other). I'm looking to buy a video card that can accept three monitors, anyone can recommend one?

I could plug two monitors in the onboard card and the third one through the USB but frankly I'm trying to avoid that as you can't really watch videos or do anything intensive in it

 

I'm using this with 3 27" monitors, happy with it.

http://www.amd.com/uk/products/workstation/graphics/ati-firepro-3d/v4900/Pages/v4900.aspx#1

 

nvidia nvs 450 has no fan, plenty on ebay.

 

Are you sure about that?
I think that bios setting is for which graphic card will be enabled
for boot up.

 

I asked Asus and they told me you can only use one at a time

 

Typically the onboard video is disabled when you plug in an external card, by default, and you can't get around it.

Have you looked at the Radeon HD5450's? They have passively cooled models. I ran one on a pci slot, and one on a pci express no problem.