"Bottom line is that that was indeed the real Imperiex in that pic and Superman had him staggered"
Are you sure? Probes wer the ones that fough mano a mano against the heroes. Mongul and him fough what they tough was the real deal but it was a probe instead. At least its how i recall it. If Supes alone left him that way how come he didnt manage to beat Imperex with the allies he had? Doesnt make sense does it.
"He took a blast from Orion."
Taking a blast is not beating him. Orion has a damn fine record against Supes.
"The only person I've ever known to have beaten Superman fairly, and wasn't beaten to a pulp in payback is Orion."
Add Captain Marvel.
"Supes was doing both, fighting and moving at high speeds"
Like every high speedster does, not FLS.