First, what you cannot tun with double 570s? Those are ~on the same level as the GTX-660, upgrading to 760s wouldnt really add too much to the performance, compared to their price.
Then, DDR-1600 is enough for everything. Get 16 gigs and youre good to go for the next 3-4 years.
Double 770s arent bad at all, but please do some research about how the SLI is scaling on the games you would like to play. Also, would consider buying double R9-290s, or one GTX780.
Also as much as im an AMD fanboy on the VGA side, i would recommend to get an i7. Not sure if that 8350 is enough for that SLI setup.