So, if you can wait another 1-2 months, the new generation of GPUs is coming out, from Nvidia and AMD. Both of them are making great strides and, based on the leaks, it could still be quite interesting.
Regarding 4K; Actually, you still have to make compromises, either 2 strong cards and micro stutters and partial compatibility problems, or 1 strong card and live with lower FPS. At max. details, 60+ FPS, there is still no card that can handle 4K. And I mean modern, technically demanding titles. Of course there are people who disagree with me and are of the opinion that "everything runs suuuuper smoothly in 4K, people only see 24 FPS anyway and blah blah blah...). My tip: Be patient with 4K, in the next 1-2 years the hardware will be ready, including monitors and connections...DVI 4K with 120Hertz... Freesync or G-Sync etc.