With SLI this game (under graphics limited situation) gets nearly 80% boost. This game was built from ground-up with SLI in mind. As a matter of fact, you don't even need a profile. It's built-in to the game engine.
The problem is, with this game you'll be 1/2 times graphics limited and the other 1/2 times CPU limited. When things are peaceful, SLI will make things smooth very noticeably. But when you have 200+ military units duking it out with all the firearms, smokes, and physics, etc. You basically get same 10+ FPS with 6200 TC or 7900 GTX SLI. I'm speaking from first hand experience.
But in general, with 7600 GT, you'd be able to play the game with all the glory @1024 or @1280. (I'd say you'll see 30~60 FPS under graphics limited situations) But for 1600x1200, you need a better card than a 7600 GT.