Do you still use some CRC DC filtering beyond the regulation?
On one picture I spotted the 22+12nF to compose the 34nF. What is your choice of 100nF? - The red Jantzens or the golden caps which resemble Obbligatos?!
Regarding your observation of quietness and stable imaging:
Imho the key to quiet ("black") background is the low impedance approach, ie. a high gm tube in front, and a rather low-ohms Riaa filter towards second stage.
More noise will render things more fuzzy and less accurate.