Good decision going to a 1151 over the 1150 ML52 - a 6600k is a newer cpu/platform than the 4690/4790k, but not much is any more $, so going to the more current cpu/MB is a smart choice.
One thing I'd like to put in is this - if you can wait a few months, do so. The new 1080 GPU from nVidia as well as new Polaris stuff from AMD will be out in June/July they have said yesterday, so spending big $ on a 980ti will mean that it'll be instantly devalued in just a few short months, by a lot, and a newer card that's much faster will be out. The new Pascal 100 series which will have HBM memory will be out shortly after the 1080 is released too, which will further depress the value of the 980ti right now.
If that doesn't bother you, get a 980ti right now, as it's still arguably the fastest card out there (even compared to the Titan it's close or faster in a few apps/games, Fury as well), and a great card, but just be aware that very, very shortly it's going to be replaced, and the price will plummet, as will resale value, as well as it won't be the fastest performing nVidia option out there any longer.