If OP wants a good CPU with good performance in multi-threaded scenario then fx8350+gtx660 sli is ok.
The 990fx based motherboards are comparatively cheaper and offer good feature-sets.
i5 3570k is quite good but then one has to compromise for gtx660 SLI.
For gaming performance with a good CPU though not overclock-able i5 3470 with hd7870 crossfireX is also fine.
If going for multi-GPU hd7870 is would be better than gtx660 SLI from gaming point of view.Else gtx660SLI is ok.
The 990fx based motherboards are comparatively cheaper and offer good feature-sets.
i5 3570k is quite good but then one has to compromise for gtx660 SLI.
For gaming performance with a good CPU though not overclock-able i5 3470 with hd7870 crossfireX is also fine.
If going for multi-GPU hd7870 is would be better than gtx660 SLI from gaming point of view.Else gtx660SLI is ok.