R9 290X 4GB vs DUAL (SLI) 670 GTX 4GB (8GB Total)

[d2warren]

At the risk of looking like a complete newbie, I would like some advice on the different options of video cards I have to choose from. I'm 99% the dual SLI configuration with 2 EVGA 670 GTX 4GB cards is the way to go but I'm just here to make sure.

Here are the options I have:
R9 290X 4GB
OR
Dual (SLI) EVGA 670 GTX 4GB cards

There is also an EVGA GeForce GTX 670 2GB FTW version that I could get. Could I SLI one of these with one of the 4GB GTX for greater performance than the two 4GBs together?

[David (PassMark)]

You really need to know what software you are going to be using to know what is the best.

I don't like SLI much. There are some compatibility issues, they use more power and make more heat and noise (on average).