Hi PD: subject to some discussion below, the most commonly seen R/C bypass is 250 ohms/5 watts and 25uf/25V. Having looked at group of schematics for SE and PP amps, the lowest R was 200 ohms (Gibson GA8 Gibsonette, parallel 6V6s) and designs above 250 ohms included the 5E1 and AA764 Champs at 470 ohms and the highest in a brief survey was the SE 6BM8 Gibson GA1RT at 680 ohms. As you know, the lower the value of R, the lower/cooler the idle current.
The bypass caps were either 20uf - 25uf (no meaningful difference) or 50uf (Ampeg Reverberocket R12R, 6V6s). In those schematics that had cathode voltages, the design objective is consistently between 16V and 19V. Finally, nearly all of these designs rely on the older RCA Tube Manual data for maximum plate dissipation guidelines; guidelines routinely ignored by Mr. Leo Fender who certainly knew his beans.
One of our BBers tele4tone started a thread recently about his
Class of 57 Amp, a design similar in concept to the Emery. I went and looked at the Class of 57 and Emery sites - killer power transformer on the Superbaby btw and neither provided an accessible schematic. Giving them both the benefit of the doubt, they had to have spent a lot of time trying to optimize a power supply for group of tubes that present such a wide range of voltage handling characteristics.
That's all 'code' for how does a fixed plate voltage, fixed bias cathode resistor, and fixed heater supply maximize tone in a group of tubes whose outputs in SE config range from 5-6 watts for a 6V6 to as many as 16 watts for a KT88? ... and what about the screen supply; sometimes at the same voltage (EL84/Marshall), sometimes not (6V6/Gibson) and sometimes regulated (6L6-6550/Guild) admittedly all PP designs?
I guess what I'm saying is that your finished product will give you a chance to listen to a variety of power tubes and that would be pretty neat but without some close figuring at least on screen supply, there's a chance that the distinction might not be a great as you expected ... not trying to discourage ... it's more about expectations. Also, tele4tone tone just posted in his own thread this morning about his disappointment with his Class of 57 .. take a look over there. Good luck! John