Whoops, yeah..typo. That should be 970, which was OC'd to well beyond stock 980 speeds. I'm still only on a 60Hz monitor, so the 970 to 1070 jump wasn't going to do a whole lot for me as I was maxing at 60fps before in pretty much everything. I found the 1070 for $330 during a Black Friday sale, so it seemed a no-brainer to pick up for the new system.
And yes, the CPU absolutely makes a difference. Sure, the i2500k was "just fine", but many things are just smoother in a way that goes beyond the FPS counter. Even games like Skyrim and Fallout 4 just glide along in a way that they didn't before, with less "hitching" and other subtle annoyances, and the 970 laughed at both of them. Games that are more CPU-bound like Star Craft 2 and Rome: TW 2 benefit even more. Just navigating around the OS, loading and switching between applications, etc, is noticeably zippier. (I'm using exactly the same SSD drive in both, so it's not that). I never said that it's a HUGE difference, but it's very welcome and more than I was expecting. I'd love to grab a G-Sync 1440p monitor and really take advantage of the horsepower, but they're all fucking matte and I hate matte with a fiery passion.