Optiplex 3020 - 4 monitors

I'm looking for advice on the proper video card(s) to purchase to enable a Dell Optiplex 3020 to support 4 monitors.

The current system supports and has 2 monitors using the ports integrated on the motherboard (a VGA and Display Port).  I am unsure if the system is even capable of supporting 4 monitors, but I would assume it would if I purchased the correct video cards.  The motherboard has three PCIe-1 slots (the small slots) and one PCIe-16 slot.

I would think I would have to purchase one video card that supports 4 monitors, or two dual monitor video cards, however, they would either both have to be PCIe-1 cards, or a PCIe-1 and another PCIe-16 video card.

If someone can point me to a link showing the best solution (if this is even possible), or tell me what I should purchase, I would appreciate it.  This is for a business system, so it would only be used for browsing and documents (no heavy graphics).

PS - I do have a Dell Optiplex 980 system with 4 monitors using two ATI HD 4550 cards (PCIe-16).  However, this is not possible on the Opitplex 3020 because it does not have 2 PCIe-16 slots.

Thanks.