Joule vzn 80 or 100 for merlins?

The Dehavilland monos that output 30 watts employs the commonly used 845 triode output tube. The Joules use 6336C tubes. There's no such thing as a "OTL tube" .... it depends on the how the output tube is applied in the circuit.

FWIW, I use about 25 watts of SET power (Art Audio Jota monoblocks) on my Merlins, and I love how they perform. It should be noted SET sounds lot more powerful then its wattage rating suggests (relative to SS, PP, or OTL circuits). The Jota monoblocks are high current animals. For the same reason, I believe the VZN100 is a lot better then the VZN80 because of its better current delivery (monos versus stereo).

Transcendant has a SE OTL. I believe it's the only one in production. It's very difficult (prior to the Transcendant, I thought it was impossible) to create usable impedance for speakers in this circuit.

The GM-70 rarely gets used in the US (mostly finds use in ex-Soviet block and in Europe). It is similiar to the 845 so it's a simple revision.