Hi Vega, I just replied in other thread but not sure if i explanied myself correctly.
i run nvidia surround same as you with two gtx 480's but i have a third video card (gtx 9800) to run helios on a fourth monitor. so far so good, no problems (apart of the frame hit but not because of helios, it happens because os surround).
my problem is to get the mfs exported to the fourth screen, i can export them to any of the other three, but not to the fourth (touch).