If this is for gaming and regular work type stuff, it is not worth upgrading; there is a performance difference; however, in terms of tangible-while-doing things it is nil unless you keep an FPS counter going. There are some newer features like M2 SSDs and such that will benefit you in upgrading, but again, that doesn't do much outside help load times a bit. Even a 900 series (2009) holds up fine for modern games as long as you have a decent GPU. The biggest differences will be @1080p; but again, if you're not a over-obsessive FPS counter watcher, you're not going to notice and you'll be able to get 60-80FPS on Very High settings in most games. @1440p and above the FPS difference narrows drastically. I have everything from a Core2Duo to an i7 7800X with plenty in between (i7 930, 960, 980X, 4770K, 6700, 6850K, i5 6600K) with cards from the GTX 690 to the 2080Ti. Gaming on my i7 960 or 980X is plenty fine with a 980Ti/1070 in modern games. Overall CPU peformance increases have not been very impressive since the first gen i7s, they are incremental and dissipate quickly once you increase resolution and the work goes to the GPU. Since you are asking if it is "worth it" to upgrade from a 2500K to a 3770K or 7700K, then answer is no, not unless you obsess about frames per second, and especially not @1440p+.