Like mentioned above, will you use this for gaming? I am highly guessing not. You just want to work on 4 displays if my guess in some sort of workstation fashion.
If your machine has 2 PCI-E x16 slots you could just get andy 2 cards that support dual displays. If you have just one PCI-E x16 slot you could look at workstation cards. OR Jaton has a 4350 dual card that has 4 DVI outs: http://www.newegg.com/Product/Product.aspx?Item=N82E16814139055