[MrFixr55]

Crosley did a similar trick in the 5C2 (and likely others) ca 1834, and really did boost the bass. The difference is tha the 1st AF was a pentode. The screen B+ was taken from the audio output plate and the higher frequencies were bypassed to ground by a capacitor, therefore supplying positive bass feedback.
+1 on transformer size, but I have a Motorola with a rather small output xformer but the tone is still rather good. the Mitchell has a 60uF input filter, therefore they were serious about filtering the DC supply.

Start with the speaker.