What to upgrade first?

I'm really far out of the loop when it comes to up to date pc parts. I am currently using a Core i7 920 @ 3.2 ghz with a gtx 670. What would yield the best results to improve gaming performance? Upgrading the cpu to a 4690k or upgrading the gpu to a gtx 970?

I assumed that the gpu would be the obvious thing to upgrade first until I saw this video. https://youtu.be/VPHw-znMOqs

I'm concerned that my cpu is becoming a bottleneck, even though I haven't noticed any significant issues regarding cpu loads reaching max. Thank you for your time.

My current build is as follows. Core i7 920 @ 3.2 GHZ, Asus GTX 670, 12 GB RAM, Sandisk Ultra II 500 GB SSD, Xigmatek 750 Watt.

@DJ419: Can you OC the CPU anymore or is 3.2Ghz the limit for your chip?

@GTR12: I could but, I feel like I might as well just upgrade the cpu at this point.

If you have the funds then you might as well grab i7 4790k and a gtx 970

@04dcarraher: I don't have enough for both at the moment, which is why I'm asking what would be better to upgrade first.

Upgrade GPU and see if you can squeeze a little more from the CPU, aim for 3.5-3.6Ghz.

I just spent about half an hour messing around in BIOS. The best I could get it to was 3.4 ghz. Anything beyond that becomes unstable. I'm not experienced with overclocking by any means so, I'm not gonna try pushing it any further.

Get 970, 390 or 980Ti right now for best boost.

Later on upgrade CPU to i5 6600K or 4690K.

Since we are waiting a huge upgrade for GPUs in the next months, I would suggest to better upgrade your CPU and mobo to a 4690K or 6600K (this might need upgrading RAM as well).

The 390's price to performance ratio looks quite impressive however, I've had one too many problems with AMD products in the past to consider buying from them again unfortunately.