Stock cooling air, and I have a GTX660 FTW Sig2 twin fan in my first PCIe_x16 slot.
Still rolling on Asus & SandyBridge here, but I wanted you to have a baseline for comparison purposes.
48c at idle seems a bit high for MB temp... z68 or x79.
My low temps are achieved by airflow through my case. What kind of case do you have? Granted if you have something hovering over a passive heatsink, its going to run hotter that the rest of your rig.
My case has 200mm front and top fans and a 120mm for exhaust, notice that they run at 700RPM or less. I don't even hear them running most of the time. They spin up if needed as do the fans on the 660, but you have to push it hard. I don't think the MB ever goes above about 44c. I've never had a reason to use anything except stock air, but if you want to OC, I'd do a nice water cooler which will give you the space for the card. Case is everything as well. The higher volume of air the cooler the MB will be, and as you can see, you don't need screaming fans to do it.
![](http://i.imgur.com/mrh0IWi.png?1)