I'm likely going to be using a Gigabyte GA-990FXA-UD7 motherboard, and an AMD FX-8350 CPU just for reference
My question is which video card should I hook which monitors to? Should I put all three monitors on one card, or move one monitor to the other card? If I put one monitor on the second card, do I have to have two monitors on DP (one on card A, one on card B) or does the one monitor on DP cover both cards?
Please don't suggest anything unrelated (switching to Intel or NVIDIA, for example. I like AMD, and I want the CPU, GPU, NB and SB to match up. I know AMD CPU's are a few generations behind Intel, and that Intel is spending AMD's CPU division into the ground and on the verge of creating a CPU monopoly, and I have no intention of giving them any of my money. Deal with it.) to my question, I just want to hear about connecting the 3 monitors to the 2 Radeon 7970 dual GPU cards. I am aware that one of those cards will support the three monitors.
I just want to know if I should hook up all three monitors to one card or divide them up, or if it matters/makes a difference.
Definitely all three to one card, as sooth1 said. Just be sure that you're using Active MDP adapters, if you need to connect to DVI or VGA ports on any of the monitors. Passive adapters won't work.
I have three of those cards - it's easy to hook up all three monitors (or more) to the same card. Great card, too.
If you ever go above three monitors, you can connect a fourth to the card, through all the ports, but to go up to six you need a displayport hub gadget. I've not used one of those but you'll find more info on them on these forums.