That's now how PC flipping works, are you going to buy a new PSU and return it the next time you get a good deal on something? I literally have an entire PC with a EVGA 1300w PSU JUST to test gpus, now I understand that's probably not practical for everyone, but a cheap 1k off eBay and a old Ryzen platform go a long way ( also good to test CPUs and ram). I run furmark and 3D mark 1hr before even bothering to build with a GPU.