Re: 807 (maybe) amplifier build.
My PA120 is 1.25K A-A. so basically the datasheet EL34 push-pull value divided by 3.
Returning to the 807 datasheet for an anode voltage of 400v class AB1 they recommend 6800R A-A, so 2.26k for a sextet. Your 1900 should be near enough - it's not an exact science.
However they quote 36w @ 400v so your sextet power should be approx 108w. This would be straight push-pull not ultra linear, and with G2 at 300V. Suggest you give it a try. Put a 10R resistor in each cathode. This will allow you to measure bias current and also act as 'fuse' in case of disaster.
Higher powers are obtainable with higher anode voltages, however the required primary impedance goes up so you would be back where you started.
The Vortexion managed 50w from a single pair with 600v on the anodes and 300v on G2, however its O/P transformer was probably 10k A-A
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