The JJ 40 watt "2A3" (also available at
www.eurotubes.com ) is actually a 300B with a 2.5V / 2.5A filament (instead of the 300B standard 5.0V, 1.2A). The eurotubes price for a MP is almost $60 less that TD, FWIW...
With reasonably efficient ( 93 dB or better) speakers, the GSG will deliver decent SPLs. Most "mini size" speakers are around 85 dB/w/m SPL.
3 watts is about 5 dB above 1 watt.
/ed B in NH