(2) 8800GT SLI Mode on MSI P6N Platinum wanting to add a PCI 128Mb Card with just one output at this point I am going to try.
currently running 4 displays and I have to get at least one more added on, preferable 2. I tried a couple cards already and they are not working, anything I should know about this config or is it best to add a couple more by USB.
Pure guess, adding the other card is effecting the RAID due to limitations of the board. Its an older board, and probably can't maintain that many connections. You can try disabling things in the bios that you don't use like firewire, parallel ports, etc. You can also try a different PCI slot if possible in case its an IRQ problem.
It not, dump those Nvidia cards and get some newer AMD ones. The Eyefinity cards from the 5 series support 3 monitors each, while newer 6 series cards can do 4 each.