Garnet GS100tRW -- Very low output power

[mresistor]

if it's only reading 0.6 ohm I'd say it's not healthy    possible shorted coil   what is the rating  8 ohms ?

[shooter]

were both the PS and OT transformers new on this build?

temp in your bench speaker and play, get physical with the cab, play, rock the cab, still good?

[Lectroid]

@mresistor,

Thanks for opining on the speaker.  I'll replace it.  The current one is 8 Ω. 

@shooter.
I think the amp is good, overall.   I like it--the Middle control has more depth than Fenders or any Marshall I've played.  It has lots of master volume. Played it this morning for half an hour and it was loud and clear, effects all working.  B+ still at 430V and bias still at -44V.  Almost no perceptible noise.  Tremolo is very quiet.  Reverb is clattery at max intensity but okay if you turn it down.  If it was my amp, I'd try a different, multi-spring 4F reverb pan.