No. The GTX 560 and GTX 560 SE are built on different GPU variants, and so are not a compatible pair for SLI. You will require two GTX 560s or GTX 560 SEs, but one of each is not a possible grouping.
You could, theoretically, use the GTX 560 as your primary GPU and designate the GTX 560 SE to driving accessory displays, but you would not be able to span games across any more than is attached to the primary GPU (the GTX 560 in this example.) Would that be worth the money? Probably not, considering that just about any secondary GPU could do the same job.
No. Only Kepler-based GPUs (GTX 600 series) are capable of driving more than two monitors on their own. Regardless of what you intend to do, if you want three or more monitors, you'll need a second GPU.
What could you use? Pretty much anything you can install in a PCIe slot. Driver support would be required, sure, but you shouldn't need to reinstall anything.
Last edited by Collie; 2013-01-04 at 05:34 AM.
Reason: Accidentally a word.
I mean, say i get a second GPU that isnt a GTX 560, I would run two monitors off my 560 and one off the second GPU, would i still be able to achieve three desktops thought windows. (Meaning i can take my mouse through all three monitors.)
Oh. In that case - sure, if that's what you wanted. Bear in mind you'd still only be gaming on two of those displays, and think of how that'll end up... With the bezels dead-center! Not exactly ideal. You'd have two accessory displays and one focus display for gaming. If that's not such a big deal, then go for it. Otherwise, spring for a matching GPU and go with SLI for 2D Surround, if you meet the requirements.
When we're talking about pushing just one monitor, the deal isn't terribly lopsided in your friend's favor, but you would be walking away with less afterwards. If you forced me to put a figure on it, I'd say the loss would be around 10-20%, and that's assuming your system and game environments are conducive to high SLI scaling in the first place.
Driving three monitors at once is something else entirely. The enormous strain of having so many additional pixels to shade and textures to render means that the GTX 550 Tis' much smaller arrays of shader cores and narrower memory buses will be quickly overwhelmed even with meager graphics settings, likely to result in something closely resembling a slide show. The GTX 550 Tis are, after all, at the lower end of mid-range cards, and Surround setups just don't work here. It's not something you can be cheap about and expect workable results.
With that, I do not recommend you take the trade. No outcome ends in your favor, not even if you were to only play on a single monitor. My advice at the very least would be to save up and purchase another GTX 560 as a companion to yours, or perhaps even buy a GTX 670, which can drive three monitors in 2D Surround all on its own (although Surround is something you really ought to always use in conjunction with SLI. The performance requirements are quite extreme for just one GPU to handle.)