The information I got regarding this was from a post about power strips that
@Dark Horse commented on. To summarize, he stated something to the effect there are heavy duty power switches built into the amps that are better dealing with the power requirements with bigger tube amps. It was noted that using the power switch on the power conditioners or power strips to power up and down tube amps and racks could damage or destroy these power switches on the strips/conditioners, that aren't rated to handle the power.
He of course could explain it in a way that makes more sense and logic, but with me that's probably as good as it gets. There is a long thread regarding the debate on power conditioners, and if you have the time to sit and read through it, his points will be there. It's actually a good read, and the reason I go directly into the wall with my power amps now, bypassing my power conditioner.. I still run my rack mounted effects through my furman.
Sorry didn't mean to ramble.