But that's the point.Titan anything is just ego-stroking for the biggest of fools with cash to burn, especially when nVidia is just going to come out with another monstrous Titan model soon after. They're glorified cash dumps. Just get a GTX 980 if you're looking to go all Hulk Hogan on your games.
What we really need right now is a solid lock on your true budget here for this rig, because it's going from under $2,000 to well over $4,000 if you're going to be throwing Titans and 6/8-core processing around.
Seriously though, new GPU architectures are supposed to be around the corner so don't go anything beyond a single 980.
Also recommended was 6-core CPU. Better for the future.
The same is for 16GB of RAM. You won't need it now, but you will soon enough. Might as well stick to 16GB and you won't have to upgrade again next year (or buy completely new sticks all together if you don't manage to find identical ones).