It has always been saying. GPU is the key to drive modern graphic/gaming/compute in desktop. Therefore, a MacPro 5.1 have unbeatable value because of its capability to upgrade. The compute or gaming power have increased by 20X or more with GPU like Titan xp vs gtx285 when Mac Pro 5.1 debuted in 2010.
Keep up with modern GPU, you don't have to go the route with the Hacintosh since other improvement can't fill the gap that brought to you by the new Pascal architecture, eg various generations of intel CPUs. No matter Mac or Windows. If you want both worlds, Mac Pro 5.1 is the one to stick with since usually people can go boot camp for gaming like me.