hmm then you're going to have to make a sacrifice somewhere. how is the 5970 a triple slot card? does it have a accelero cooler on it? but even if it does, that aus P8P67 Pro can still accomodate two triple slots cards. there are 2 slots between the 1st pci-e and 2nd pci-e, everything should fit. unless you want to leave an additional slot for breathing room beneath the 5970 if it were to be in the top slot?
The 5970 has an Accelero cooler on it and I can't fit a dual slot card in the bottom PCIE slot because my case doesn't allow it. I'll have to bust out an angle grinder and grind out part of my case to do that.
The only way I've managed to get the 2 cards to work is to Crossfire them. Yes, I know that this will cause a decrease in my hash rate.
I don't think my motherboard has the option to change the primary display card as I've had a good look through the BIOS and motherboard manual and can't find anything like that. I have tried connecting different monitors to each card and it will only display from the top card.