It was your motherboard, it might have just been a EFI/leagcy setting, or it might not have supported it at all. I've had R9 280X, 290, GTX 770, 960 and 980Ti all running fine on H61 and Z77 boards with an i7-2600 and 990FX boards under PCI-E v2 no problem. Going the other way (old card new mobo) I had to set a PCI-E specifically to v2 was an R9-270X when plugged into a Z87 board, for some reason it wasn't stable under PCI-E 3.0.
Newer hardware is always the better option. If the OP needs to spend money then buying a 4/5 year old CPU that has been heavily over-clocked doesn't make much sense - esp when its not going to be a massive step up over the existing CPU in terms of gaming performance.
I appreciate everyone's input. I seem to be getting a range of replies from "it's still a viable option" to "look for a new platform. Maybe rephrasing my question would help. I wanna build a ~$800-1000 Cad PC. In terms of bang for buck for 1440p gaming and possible VR, is this my best CPU? I can get an 8350 new for just under $200, but the i5 beats it in gaming so I don't see a point. That leaves the 6600k; which while being faster removes another near $200 after tax from the rest of the build... if anyone knows where to grab a cheap 6600k in Canada do let me know. 800-130 leaves 670 for the rest of my parts, or 800-300 leaves only 500. http://m.ncix.com/products/sku/110592 appears to be my best bet but it's not a K part.
