3DMark
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.
PowerColor's core clock speed might be slightly slower than an R9 295X2, but it has a faster frame buffer, which appears to be going down a treat with the synthetic 3DMark benchmark.