Probably the most significant for your application is the AC filament power of the Stereomour. There will be a little 120Hz hum, IIRC we see around 2mV depending on the symmetry of the individual tube. For some reason, 45s are a bit quieter, maybe 1.5mV. This is usually inaudible, but with really high efficiency speakers you could hear it. We do not at this point have a DC supply available.
Sonically, the Paramount has shunt regulated power for the driver; there is no provision for another tube to do that for the Stereomour. Also, in 2A3 for the Paramount is direct coupled, which makes an audible difference; the best option for improvement would be a better coupling cap such as the (expensive!) teflon V-cap.
At present there is no fully-satisfactory Magnequest iron available to upgrade the Stereomour, whereas there is a good package for the Paramount. I'm very happy with the stock parts in both amps, but I make no pretense of my designs being as good as Mike's! In particular, we are not able to offer nickel cores.
The parafeed cap can be improved in both amps, of course. And there are always minor upgrades to the power supplies that people have tried and found helpful. And of course we continue to look for improvements in all our products. :^)
I hope that is helpful!
