Both the GTX Titan and the GTX 690 will easily run shaders on Max. If that's all you want you could go for something much, much lower like a GTX 5xx, even. It'd run it just fine.
Saying 5xx is improper seeing a GTX460 is better than a GTX 650.
Don't go by the first number while on NVDIA, the first number is the series, the second is the generation, which mostly measures it's power.
Also, you'll literally be a bit too much out of the line with a GTX Titan for just that, I am on GTX 460 and I can still run it on max. The only advantage you would get is even better FPS in the case of more bricks.