Myles, I read your review of the Ruby Tubes EL34B-STR and thought I might try either a pair of those or a pair of the GTKT66 HP's in this JTM45 type thing. I was thinking a #4 rating for the KT66's, but how does one specify an equivalent power rating for the Ruby tubes? I was planning on buying from Antique Electronic Supply who do some type of matching for $1 per tube.