Your i7-4790K will be a good pairing with a GTX 1060, or an RX480/580, or a GTX 1070, or a GTX 1080, or even a GTX 1080Ti.
The choice of the GPU would now entirely depend on the monitor's resolution and refresh rate you are using.
1080p/60Hz --> GTX 1060 or RX 480/580
1080p/120Hz or 1440p/60Hz --> GTX 1070
1080p/144Hz or 1440p/120Hz --> GTX 1080
1440p/144Hz or 4K/60Hz --> GTX 1080Ti
*The above guide considers ~AAA gaming in High-ish to Ultra-ish settings (but also depends on the specific games and in-game graphics settings)
For the PSU, the EVGA 850W is overkill for your i7-4790K + any of the GPUs mentioned...