Gtx 1070 or 1080
Gtx 1070 or 1080
Check if your current setup is suitable for running at full GTX 1070 or 1080. You mentioned using a 1080p monitor at 144mhz and have an ASUS Z87 Pro with an I7 4770K, 16GB DDR3, SSD+HDD, and a GTX 770 upgrade plan. Your power supply is a 650W silver certified unit. Ask if these components can handle maximum performance and if overclocking is possible.
The GTX 970 meets your needs, and costs are decreasing over time.
If you prefer a GTX 1070 or 1080, there won't be any clear guidance until the specifications are announced and tested.
A GTX 970 can do what you require, and prices have been dropping lately.
If you're set on a GTX 1070 or 1080 then nobody can give you an answer until the cards have been released and benchmarked.
He suggested a 970 would work for you unless you intend to move into 4k gaming or VR later. If you're okay with 1080, you wouldn't be concerned about buying it, as you'd be paying more for unused hardware. The 1070 would cost even more than necessary. But between those two choices, the 1070 seems more suitable for your current setup. I think a 970 is better because prices will likely drop once the next generation arrives.