@strats From PAP's site for the Trio 15s (Vox PiFe): "Technical Data
- Sensitivity: 94 to 96db (in a typical room)
- Nominal Impedance: 8ohm
- Frequency Range: between 29 to 32hz – 19Khz (in a typical room)"
From Lampizator: "64 steps with Upto 6Vpp output" (I'm sure Lampizator can give you the output voltage for their single ended version, but it's probably safe to assume 'half' or ~3V)
Given the easy load your PAPs represent...
AND Conceding that the 30.8 is probably best driven using it's XLR inputs,....
I'd save the money on the 'Balanced' version of the Golden Gate and put the savings into a higher calibre / performing single ended cable and an upgraded power cord and outlet to the 30.8. Any additional savings can be invested in tubes, as you pointed out, or elsewhere.
All the best.