3DMark Fire Strike
3DMark is the latest version of this hugely-popular synthetic benchmark. Making use of DX11 features such as tessellation, compute shaders and multi-threading, it provides modern-day results and is available as a free download.
Spending a little more - £215 or so for the EVGA GTX 1060 6GB or Sapphire Radeon RX 480 8GB - gets you an additional few per cent in performance. Going by these charts alone, the PowerColor pricing is pretty good.