First off, I might not sound like it but I'm trying to help. Secondly, your question about SLI compatibility is misguided. All games are SLI compatible. To a game, there is only a graphics layer API like DirectX or OpenGL. It does not see 1 x Radeon HD 5850 or 2 x GTX 570 or what not. That was the point I was trying to make.
http://www.slizone.com/object/slizone2_game.html . So I might not be the best person to advise you on an SLI setup, but maybe I can correct a few of your misconceptions.
Also, I asked what you were using it for because your monitor is not listed in your sig, and depending on what resolution you are playing your games at (even the high end ones), your SLI setup will be a waste of money and not contribute anything more than SLI 560s or maybe a single 570. If you want scalability for later released titles, that's a whole different story. It's also the kind of information I was asking you for.
And I responded to your question about SLI micro stuttering, which you could have found out by spending some time to read posts in this forum or doing a google search.
Sorry for being callous but you sounded uninformed and ready to drop > 600$ on pieces of hardware that you haven't done any research on. However, based on you signature, it does seem like your GFX card is the hardware component that is bottlenecking your gaming performance, and maybe it is a good upgrade for you.