Yes and no, Q6600 is indeed bottlenecking GTX760 for many games which requires stronger processor.
Crysis 3 is quite processor intensive. Crysis 3 shows even better fps on processor with more than 4 cores/threadings.
As time goes by, Q6600 will bottleneck GTX760 more and more.
In general, yes, you will see more fps.
I recommend to put Q6600 to retirement as gaming system.
i5 4670k is a nice choice (the most efficient gaming processor in my opinion), if you decided to upgrade your system.
You will need i5 4670k, an 1150 mobo and at least 8GB RAM. The rest you can keep.
It means, yes, the bundle on your link is OK.
An extra recommendation which will boost your new rig is an SSD. This is still optional but you will feel the difference.
I would also recommend an after market cooler for OC, especially since the i5 4670k + Z87 mobo are designed for OC.
sorry I missed the GPU SLI question, I would not SLI GTX760s and combine it with Q6600.
With i5 4670k I would, bu tnot with Q6600.