Upgrade ideas

I currently have an i5 750 clocked at 4 GHz, 8GB of DDR3 1600mhz RAM and two 6870s.

I'm looking only for 1080p, 60fps. I have decent matching monitors and not looking to upgrade any time soon so no push for 144hz or 4k.

Is it worth upgrading the video card? Is the i5 750 able to keep up with any decent card of today at its current clock?

Or could the 6870s fair better with a stronger backbone? Running afterburner it shows the CPU at near 100 in any intensive game. Within the next year I want to have a completely new build all said and done, just trying to see what's the best first practical step.

Budget for the first phase is about 300. Thank you.