GTX 670 SLI, need some advise

[sniper2606]

Just to keep it short i have a i5 2500k OC to 4.0 with a single GTX 670, i was wondering if i could SLI and not bottleneck anything? my current power supply is
XFX Black Edition XPS-850W-BES 850W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS SILVER.

Specs:

Windows 7 64it
8Gb ram Corsair Vengeance
SSD
Asus sabertooth z77

My pc does ok with games like Max payne 3, crysis 3, starcraft 2, most wanted but there is always that frame rate drop that bugs me, i just wanna play those games at max levels.

Just mostly worry about my PS, its a bit old

Opinions?

 

[clutchc]

As long as you match the cards for model, speed, and memory, it will be great. The i5-2500k won't be a bottle neck.
http://www.tomshardware.com/forum/245454-33-crossfire-faqs