I'm currently rolling with the following:
EVGA P55 FTW
i7 860 @ 4.0Ghz w/ Swiftech Apogee XT
Corsair Dominator GT's 4GB
2x EVGA GTX 285's
3x120 Swiftech Rad in top of HAF 932
DD CPX-Pro
Corsair TX750
I had a 780i FTW and 790i Ultra. I would gladly go back in time and smack my self silly for purchasing those.
If you have a 790i, return it, ebay it, or just give it to your grandma. Go get an i7 based system and run SLI on it.
Don't run SLI if you only plan to run sims.
The 197.13's work fine on BS, and I will be testing them with FC2 later tonight.
Also, I always disable SLI for BS, FSX, and LOMAC:FC.
Really, those GTX 280's will just turn your room into a hotbox. You'll only need one.
An E8400 or Q9550 will easily push a GTX 285 at stock speeds, especially with just playing sims.
If I was you, I would be less worried about GPU's, and more worried about getting a CPU that has more cores. That's just me, though.
You could probably unload those GTX 280's and that 790i Ultra and get an X58/P55 + i7 + a single GOOD GPU, with the money you would save from having to get a monster PSU to push those old-school 280's.
Again, my opinions.
If you really want SLI, don't go past 2 cards. Most all games don't scale well past 2 cards, especially sims.
Good luck, and have fun.