Excellent explanation of often poorly understood power supply issues, particularly regarding the use of chokes. Like you, I'm also a big fan of "iron" in a HVDC supply. For many years, audio power supplies were more or less an afterthought to the audio circuitry. A lot of the mushiness and euphonics attributed to tube gear was directly related to the floppy, high impedance of cheap and under designed tube rectified power supplies. Conversely, a good portion of the flat, cold, harshness attributed to early solid-state gear was the result of power supplies that consisted of nothing but noisy solid-state diodes, a pair of giant electrolytic capacitors, and simple resistor. I'm curious to see your shunt regulator. On one hand, with the minimal and balanced current draw of the SRX circuit, one wonders if it would make any noticeable improvement over the already very effective LCLC filters you're employing. On the other hand, because of the minimal current draw of the amp, the SRX seems like an ideal candidate for a shunt regulator experiment. Generally, I prefer shunt over series regulators. Sometimes I think that solid-state series regulators can add add a glare or harshness to some circuits. Shunt regulators, whether tube or solid-state, don't seem to have this problem. One thing you might want to consider if space is no problem is swapping the electrolytic caps for some PIO motor-run types. At least with class A single-ended tube circuits, it can make a noticeable improvement.