For what it is worth I used to have the p8ltd (now have the c8ltd) and have driven them with the integrated nuvista m3 (tube preamp ss output). This I have found to be a superb combination. I have a friend who drove them very well with the audioresearch 100 watts. He ultimately switched to the nuvista as well, which he preferred over having to retube his ar. Callloway who posts hear drove them with tenors but switched to goldmund. I'm not sure if that says anything but would also be curious about what others have done.
Gary
Gary