The 4790k upgrade is worthwhile.
The 4790k upgrade is worthwhile.
I'm facing a comparable setup with my UK rig, which features a 4670K and is considering a 4790K upgrade. It previously had a 970 chipset until I sold it two years ago. **EDIT** While drafting this, I realized the CPU support details for the Z97-P motherboard you own. Since I left a hint about this, it’s important to note why the 4790K might not be a good choice. Your board differs from my Z87 Asus Haswell board in that it uses the Z97 platform, which came with the Haswell refresh CPU (Devil's Canyon). This means it supports the 2 Broadwell processors, unlike my setup. I’d really think about the i7-5775C. Anandtech published a thorough article about it three months ago—definitely worth checking out. In short, it’s not too far behind the 10900K in some gaming benchmarks, though results aren’t conclusive and I’m still unsure what to take away. Still, it could be worth exploring, even at the same price point as the 4790K.
Spoiler: The catch is that used 4790K CPUs are still priced well above $100, which isn’t justified given the current market. Intel’s ARK lists a recommended customer price of around $350 for retail, and on eBay they’re selling for $130–170. That’s a lot more than what you’d get for your rig. Even the older 3770K is hovering near $100, which feels too steep. The main advantages that matter to me are Hyperthreading support and VT-d compatibility. The 4790K also offers VT-d, so virtual machines could run on it—something a 4670K can’t do. For your specific board, the 4690K already supports VT-d, making it a better fit. Also, DDR3 memory is more likely to work with the 4790K than with the 4670K.
Broadwell CPUs don’t offer much improvement in performance, especially since you’re still using a 4-core/8-thread processor; upgrading would require new RAM. Unless you can find one for under $75, it doesn’t seem worth the effort.