1. The 3570K does perform noticibly better than the i5-760
2. An i5-3750K gives you better overclocking options
3. A newer mobo would give you USB 3.0
1. The biggest is, Ivy Bridge is set to be the final generation CPU on the LGA1155, next year Intel will be introducing Haswell CPUs on the LGA1150 Socket with no backwards compatibility.
2. No real feature upgrades that I can tell from your old motherboard other than USB 3.0.. Yes, a new Z77 board will have PCI 3.0, but theres no practical advantage to it.
3. You already have a fairly decent CPU, and for gaming the CPU doesn't matter quite as much as the video card, will the CPU hold the GTX 670 back? A little bit, but even a cheaper Phenom II could comfortably run a GTX 670.
I'm sure others might have other pros and cons but thats what I can come up with on the fly.