Way back I used an A-Power AK 680 PSU, my opinion of that product, i now call it counterfeit
After roasting it half to death, i bought the Corsair TX850V2 which is more suitable to SLI setups
 
For a single gaming class card, 650W is probably enough to cover even the GTX 680 SC etc, the 850W PSU I own is capable of running GTX 680 SLI 
 
I noticed that models of the GTX 950 are available with slot power and up to 8-pin PCI Express power. Clearly this card is targeting the overclocking market. I usually buy higher up the market primarily as they cards can play games better.