If you hit 'Esc' during the copyright screen, does it show any further information?
If it is hanging on something that is getting logged, you could boot back up with the old processor, and retrieve the System Event Log (SEL). Paste it here, it might have some indication as to what the system is hanging on.
Esc key has no effect. Reverting back to the old processors, which worked fine for the BIOS update, also has no effect.
if you can't even boot with the old processors, it sounds like you've tried everything i can think of. other than pulling AC power for 20 seconds to reset the BMC ( unless you've already done that), I can only think maybe contact intel support for a replacement.
Thanks for the suggestions. I spoke with Intel support, who helped me determine that there was a problem with CPU socket #2 after the firmware update. RMA was the solution.