Yeah, that PSU will work. The 8600s don't use up too much power so you would even be fine with a good 450-500W unit for that system. An Antec earthwatts would be a good choice, as would this FSP blue storm II
Even with my previous choice, it is cheaper in price. Is FSP Group a pretty prestige company compared to Thermaltake , OCZ. Ive noticed a lot of threads refer to enermax or silver....stone? or PC cooling or whatever that one was.
The FSP group, also known as Fortron, makes pretty good PSUs. Their main business though is being making PSUs for others as they are one of the few PSU manufacturing companies. Despite the fact that they generally make high quality and efficient PSUs, they have not been too successful in marketing their brand and have lately been eclipsed on the top end by others. Check out PSU tiers to see how various PSUs compare
Well, I'm pretty sure that the 8600GTS needs a PCI-E adapter, so since both of the Corsairs only have one you will need to use a PCI-E to molex adapter for the other. The PC Power & Cooling has a 6 pin and a 6+2 pin so that would work just fine. It's a great PSU, but it's a little pricey.