I ran the firmware upgrade referenced in these fora that was p[osted over on netkas. Other than a few a few moments of worry as the screen stayed gray then black, it went as slick as snot on a door knob. Boot ROM now shows 21.007F.B06 (SMC is still 1.7f10). I'm currently running 10.7.5 on 2 x 2core 2.66 Xeon & 8GB RAM. I still need to see if the the second riser is bad as the last time I tried loading it with 8GB RAM the Mac Pro wouldn't boot. GPU is a NVidia 7300GT. So, can I easily upgrade beyond 10.7.5 now? I ask as so many app and even Apple Radio stations are crippled by anything older than 10.9 or 10.10. Hopefully in a few years I'll be as proficient on my Mac Pro as I was on my homebrew WinTel box. Thank you much.