You need a pair of Raytheon VT-231s in the rear sockets. The front sockets will then be able to flavor your music/tone. For a full juicy presentation, try RCA VT 231s(lighter), or Sylvania VT231 (fuller). Best neutral tube is the 1952 Sylvania 6SN7GT, or TungSol round plate 6SN7GT.
Sylvania 6SN7W is a great tube, and very dynamic.
Sylvania 6SN7W is a great tube, and very dynamic.