2 Nvidia Cards - NO SLI?

Ok, so I currently have a 3 Monitor setup. On my GTX670FTW I have a 27" IPS panel at 2560x1440 and I have 2 22" LCD mounted vertically (1080x1650). The 27" and one of the 22" monitors are running off my GTX670, the second 22" is running off on-board video (i3770k). My question is, if I were to purchase another card could I set it up without SLI running and have one card running my two 22" displays, and then my other card running the 27" display? Is this possible, if so is it a going to increase/decrease/not change performance? Would it be better to use SLI in the case of multiple monitors, one of which is super high res? Any input would be appreciated. 

Jordan.