Since I haven't bought any parts yet, what are the actual SLi advantages vs a single card? My computer will be built for gaming and some editing/3D modeling here and there but mostly gaming. Looking to run anything i throw at it and have every game 60+ fps with everything maxed, and i mean everything. Trying to benchmark it to be able to handle crysis 2 and bf3 60ish without dropping frames too much ( Is that even possible with these three cards?). Since my current screen isn't 120ghz can someone also recommend a good gaming one that has great quality preferably under $220. I WILL NOT BE OVERCLOCKING.
I would suggest getting the one 670 or 680 (assuming you are not looking at AMD cards since those currently have great performance to money spent ratio). Then see how it runs in your system if you need more power pick up another one. I would rule out the 660ti even though they are great in SLI it better to use one higher end card as that leave you room to upgrade to SLI/Crossfire (AMD) in the future with getting new cards.
Advantages are you can boost your graphics by adding another one, often cheaper from older generations. Disadvantage is microstuttering and random driver incompatibility. Except AMD with 3rd party Radeon Pro, which seems to minimize microstuttering on a per game basis