The one issue I can think of that you might have it that the motherboard, being of an age that it won't have PCI3 slots on it... may not be able to supply the operating power over the PCIe slots for all the cards you use. (Difference between the communications power over the pins, and the actual hashing power supplied by the 6/8 pin connectors.) You MIGHT need to get powered riser cables if you run into problems of the system crashing under what otherwise should be valid working conditions.