i have a gaz87x OC motherboard and i have been using a gtx60 dc2top -asus- for half a year. just yerstyerday i bought a gtx660 dc2 oc edition -asus-. i have the latest drivers properly installed on both cards and the sli bridge on. the control panel sees both cards but the enable enable sli option neither the green line under picture of the u/i's shows up. i am using a 600 watt psu. what can i do to get my cards to wprk on sli properly?