I had a telephone conversation about biasing with the tech support guy from Cary (this was a few years ago when you could actually speak to someone from Cary on the phone about issues) related to a Cary V12 that I was taking out of hibernation, and in the course of the conversation he told me that it wouldn't hurt it at all to bias it without a speaker load hooked up. That typed, I put a load on it anyway.
Also, I remember a couple of ARC VTM120s I used to own, & the guy from ARC told me to NOT have the preamp turned on when I biased them.