Yep, got the 4,1 here with 5,1 firmware it'll stay with me for many years as it's the ultimate load it with backup drives and cards Mac I've got.
Right now, it's basically a dedicated Grand Theft Auto 5 system dual booting Windows 11/OS X 15.x and an ATI RX590 GPU. Recently picked up an EVGA GTX680 (the one that can be flashed), which I'll set up soon and see how it fares.