Using SPECViewPerf's SolidWorks view-set at 2560 x 1600, the V5900 was 10% faster than the V5800. The FirePro V7800 results were not available, as it could not successfully complete this view-set with the GPU and this driver configuration.
While many people will likely not be running the Unigine Engine and any games it powers on the FirePro hardware, this OpenGL engine with native Linux support happens to be the most demanding OpenGL 3/4 benchmark available on Linux at this point. Sadly though, with the Cayman-based FirePro V5900 the frame-rate falls behind the V5800.
Likewise, with Unigine Heaven, the V5900 performance falls behind the V5800.