So, do you have an AGP board with 3 or 4 PCI slots or a PCIE board with 3 PCI and 3 PCIE slots? You'll either be using 4, dualheads or involve 1 or 2 quads.
Is there a dual head for pci slot and can i use two at a time plus my regular dual head video card making that 6 . Would the computer be able to handle all that extra hardware ?
Yes, and yes. You just need to be sure to get PCI cards compatible with your AGP/PCIE card. However, there are not a lot of dualhead PCI cards. Even less if you want them to run DVI and/or >1280x1024.