Re: 6970 or 560....
My qualms with SLI are this, when I have all 4 screens hooked up (three 2007's and one single 2560) the driver itself will crash or cause a bsod at times depending on what i'm doing graphically. Hence why I want to go to ATI or at least may go ATI to see how well they handle multimonitor setups.
I could go into detail, but can't at the moment as i'm getting ready for work.
Keep in mind before you respond, my rig is stable as hell when using the single 30inch dell; its only when I have the 2007's enabled when I see any sort of trouble and its rare, but it does happen.
EDIT: Also I don't like that I am limited to 3 screens in tri-sli which leaves my setup useless because I have to run one gpu as phsx to power the other two screens. (285 SLI powers a 30in and 20in dell, 1x 285 powers two 20in dells.)