Glovernator :
I currently have a Z77 sabertooth motherboard which means it only accepts socket 1155.
Is it worth buying the i7-3770k and overclocking on the current motherboard or purchasing a new socket 1150 motherboard along with the i7- 4790k.
What's your current CPU and what are you using it for? Are you sure it's holding you back? If it's an i5 or i7 and you're gaming, it's almost certainly NOT holding you back at all, and you'd be better saving your money or upgrading your GPU.
If it is an i3/pentium/celeron or you have some particular need to get every bit of performance you can, there's between 5 & 10% difference clock-for-clock between Ivy Bridge (3xxx) and Haswell (4xxx). Maybe a 4790K would get you 15% better performance, at the cost of a new motherboard AND (if you have an OEM Windows copy) a new copy of Windows.
That's not worth it in my book unless you can get a good price for your current gear. If you can sell your CPU+Mobo+RAM, you'd be better looking at a new Z170 build with an i7 6700K. At least Skylake gets you several "next gen" features like M.2 slots and DDR4 RAM (which isn't actually helpful now, but makes future upgrades easier).
I'd still vote for either keeping what you have or (if you have a valid reason), going for a 3770k... unless you can get a good second hand price for your current components.