I have an i7-3770K, and have built many computers.
Upgrading beyond an i5-3570K@4.2GHz is a waste of money IMO. A few titles would be slightly faster, and very few would be noticeably faster like Fallout 4 which is poorly optimized.
(Future proofing is pointless when you don't need anything better at the moment. In fact, with the shift to DX12 games we may see minimal need for a CPU beyond the i5-3570K for the most part. A few games may add in code that a better CPU can utilize but why spend the money now? Best to wait, and maybe even get an AMD Zen 6C/12T or 8C/16T CPU later if the value makes sense)
There are much, much better places to invest your money:
1) GSYNC monitor (not necessarily now, but save up)
2) GTX1070/1080. Performance results->
https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080/26.html
I'm buying a GTX1080 (Asus Strix or similar) when prices drop to $650USD or so.
*With a GTX970 now, you can expect about 2X the performance with a GTX1080. Is that worth the price? Up to you. I'm coming from a GTX680 so it definitely is to me.
Of course the GTX1080 is also more future proof with better DX12 support than previous NVidia cards. Here's some info, but ignore the comparison to AMD because we just don't have any software yet that is optimized towards NVidia's new cards.
http://wccftech.com/nvidia-geforce-gtx-1080-dx12-benchmarks/
Up to 1.6X faster for VR, and some cool features like Ansel for 2D/3D snapshots though this is for future games as it needs a plugin.
FAST SYNC is also coming to most current NVidia cards (works on the GTX600 forward, not sure about GTX500). I tried it out and it works (not officially released). For games you can get at least 2x the FPS of your refresh rate (i.e. over 120FPS for 60Hz monitor) you have less lag in the games. The screen still updates at 60x per second, however you output frames from the GPU as fast as possible with the last full frame created being shown (so game is more responsive than normal VSYNC).
3) Stay away from multi-GPU.
4) Buy an SSD. Something like a Samsung 850 EVO 256GB
- either clone Windows to it or put a clean install on it. If doing a clean install plan carefully
- if you don't have Windows 10 get that (free upgrade expires end of July)