I am not too tailed or interested with what this Troels Gravesen does but his use of off the shelf Lundahl with two 6C33C anodes is kind of fun to watch.

http://www.troelsgravesen.dk/AudioMirror-6C33.htm

He uses Audio Mirror DUAL SET amps inspiration. I dealt with Audio Mirror and I have no high opinion about those amps sound but still, if one needs more power than to do what this guy from Denmark does is one of the ways to go.