I've read the sticky here and checked YouTube but would prefer an opinion based directly upon my question.
I'm running a modest setup with Intel 2600, 8GB RAM and one Gigabyte GTX560 SOC card on an ASUS Maximus IV GENE-Z. I occasionally play BF3, FSX and other similar games. I've no experience of trying to run a second GFX card in SLI, if I buy another Gigabyte GTX560 SOC would I notice a better frame rate on things like FSX (everything else already seems to run fine with what I have already on full resolution with everything maxed.
Also I read somewhere that the two cards would easily use around 500w of power - I'm using an Antec CP-850 850w PSU, would this be sufficient?
I would give that cpu a bit of an overclock. I was always under the impression that FSX was more cpu bound then video bound. I am not saying more video does not help, just not sure how much you will get.
That said, your board is more then up to SLI if you want it. While some games do not get a boost from SLI many will and as new games come out, profiles for those games are added to the Nvidia driver sets to help the cards work together on new games.