Z68 sli + new power supply opinions wanted

Here is my current setup

Intel Core i5 2500k
Asrock Z68 EXTREME4 Gen 3
EVGA Nvidia Geforce GTX560Ti FPB
Corsair Vengeance DDR3 1600 8GB (2x4)
OCZ Vertex 2 90GB SSD (boot/game drive)
Seagate Barracuda 500 GB SATA II
LG 12x Super Multi Blue WH12LS38
CM Storm Sniper
Corsair TX650 PSU
Corsair Hydro H100

I'm trying to decide whether or not I should go SLI or not. Currently my power supply does not come with 4 PCI-E power connectors probably because it would have a hard time supporting two cards requiring 2 each. I have my eye set on the Corsair ax850. My current card can only go 2 way SLI so I don't need a 6 connector PSU. Was curious what the thoughts were on that and in terms of SLI it looks like the z68 chipset only does SLI in 8x is that normal? and will I run into performance loss when I play games that don't run with SLI?

I know that people will ask what games I play so here it is.

Starcraft II, WoW, BF3, Arkham Asylum/City, CS:S, GTA4.