For that budget, you can nab a GTX 1080 at or under $600 easily on Newegg. As the GTX 1070's have gone up in price a bit, I'd give it a "passing look" for that reason only.
This PSU calculator is a fairly accurate tool that will give you an idea of what your existing (or would-be purchased) PSU would need to be for your entire system: https://outervision.com/power-supply-calculator
For that budget, you can nab a GTX 1080 at or under $600 easily on Newegg. As the GTX 1070's have gone up in price a bit, I'd give it a "passing look" for that reason only.
This PSU calculator is a fairly accurate tool that will give you an idea of what your existing (or would-be purchased) PSU would need to be for your entire system: https://outervision.com/power-supply-calculator