This is an interesting thread! I'm using 'valve technology' brain cells that haven't been exercised since the 1970s and 80s when I did repairs for Cascade Music in my spare time.
Replying to Roger Cook's point about where the HT feed for the output valves is taken from (before or after the choke), the answer seems to be 'it depends'. I went to my dog-eared folder marked 'Amplifier Circuits' and flipped through at random.
The Vox AC30 (4 x EL84) and AC100 (4 x EL34) both take their feed to the centre-tap of the output transformer from before the choke. Likewise the Marshall Major (4 x KT88), the Marshall Bass 100 (4 x EL34), the Sound City 120 (6 x EL34) and the Fender AB763 Twin-Reverb (4 x 6L6). This technique obviously reduces the size of choke needed, and the push-pull output valves will tend to hum-cancel.
On the other hand, Selmer owners were expected to be STRONG, since the Treble & Bass 100 (4 x EL34 and two GZ34 rectifiers) fed all the HT through what must have been a massive choke. Likewise the Zodiac Twin 50.
Down-market, the VAMPOWER 100 (great name, wonder what happened to them?) (4 x EL34) economised by having no choke, but fed all the HT through a high-wattage resistor. That '100' might have been a bit optimisitic.
All this is great fun, but do I use a valve amp these days? No thanks! My Fender 100 watt semiconductor amp has that great clean Fender sound, 2 x 12" speakers, real spring reverb, is very loud when it needs to be, but can be picked up easily using the single strap handle.
I'll leave the fun and games with valves to you other guys.
Ray