Hey PR - I can’t believe this thread did not attract any response till now …
I recall a few posts where x2 P10’s were recommended, though “you could get away with one”. From previous experience, I also know that certain amps - notably those using switch mode power supplies - are extremely demanding on a regenerator (something to do with “power factor”).
So when my BHK 300’s; BHK Pre and DMP finally arrived a week ago, I did not even try to hook up the 300’s on the P10. Straight to the wall outlet it was gonna have to be, or so I thought.
Then, a few days ago, friends visited and wanted to listen. I was devastated when the 300’s repeatedly went into protection mode … have I blown them? On a whim I pulled out my multimeter and checked the power … 187V [in a 230V country!!!]
Tonight, I thought what the hell let’s try it anyways. So now, connected to the P10: BHK 300’s, BHK pre; DMP and DS. And the P10 hardly breaks a sweat!!! Seldom over 40% on the loudest passages. Exactly where I want it, because I believe in headroom … especially with regenerators. [Call me superstitious, but I’ll NEVER let my P10 run hot enough for the most sensitive part of my body (LOL) to be uncomfortable … let alone my hand, if I put it on the P10 lid].
I do believe a “wiki” of sorts on what a P10, 5 etc can handle will be extremely helpful. Difficult to implement? Maybe the Elks among us could come up with an idea … 
I think Gregg likes this combo! 