I'm surprised no one has mentioned Kevin Carter's superb ST-70 upgrade, with Lundahl transformers as phase splitters, a modern power supply, and (mostly) class A operation. My impression is that he is retired and no longer offers the kits, but his webpage about them is an interesting read:
http://www.kandkaudio.com/power-amplifier/ (scroll down to the ST-70 section)
Here is a European version of the VTA circuit with auto-bias:
ST-70 & AB, ultimate ST-70 VTA upgrade kit, auto bias
www.audioamp.eu
As SIY suggested, an EF86 as input is a much better choice than a 12AX7, and here is a board using EF86 inputs:
or a complete amplifier kit:
http://www.triodeelectronics.com/st70buildkit.html
My ST-70 is original, except for upgraded coupling caps, a few resistors, and a new(er) electrolytic can. It has never failed in the decades I have used it.
However, a couple of years ago I was fortunate to find a pair of Atma-Sphere M-60s, used, in good condition. They are more neutral and transparent than most amps, whether SS or tube, and they have more glowing tubes than anything else.