is everything working properly?
also, not tryin to bash your set-up in any way....
but...
why did you decide to sli 2x 8600's?
one single 8800 series or 9600-9800 series would run much better than the 2 8600's at about the same price as 2 of the 8600's.
single 8600 gt average 3dmark score of 4200 (average cost $70 each)
2x 8600 gt in sli average 3dmark score of 8400 (average cost $140)
single 9600gt average 3dmark score of 10,000 (average cost $100)
single 8800gts 320mg (the cheapest one)average 3dmark score of 9100 (i have one of these, i score allmost 10,000 with no oc) (only one i could find was $90 bucks)
single 8800 gt avearge 3dmark score of 11,000 (average cost $150)
single 9800 gtx average 3dmark score of 12,000 (average cost $180)
all 3dmark info came from toms hardware
all prices (averages) came from newegg
as you can see, the 9600gt would have been the best solution for youl. (better score and 40 bucks cheaper)
good luck.