You asked for "the very best builders" for a push-pull amp. That would definitely include Fred Volz. I have a custom pair of his push-pull Vita monoblocks that can take 6L6s, EL-34s, 6550s, KT-66s, KT-77s, KT-88s and KT-120s. I recommend them highly. Fred is also a great guy and fun to work with. Here's a link to the Custom page on his website:
http://www.emotiveaudio.com/Custom.htm
http://www.emotiveaudio.com/Custom.htm