OK, I am catching up with this thread after reading the last 51 of 83 responses. Forgive me if I am asking Mphnkns something that has already been covered: Have you explored the power source issue, and specifically the outlets (receptacles) that the FS is plugged into? I had the PS Audio outlets/receptacles and they seemed overlay a kind of glare that might fit into the same band width and quality on brass that you refer to. I installed the current FIM outlets, and bingo, glare gone.
If you happen to be using a power conditioner, try not using one at all and see what happens. Again, sorry if this has already been covered.
Also if you have acrylic shelves, that could possibly also create a similar, brassy sheen effect. I have taken to putting a board of 5/8 MDF and Aurios bearings between the acrylic shelves of my Arcici Suspense Rack and the FS main unit: (from bottom up) shelf, MDF, Aurios, FS. Big help in creating more focus and calming down a slightly splashy quality on crescendos. I do the same under the CDP.
On the Paramount Plus score, I happen to have recently upgraded my 4.0 model to the 4.0 w. Paramount Plus upgrade and I couldn't be happier. It's not the full-on Paramount Plus model, just the 4.O w P Plus upgrade. Very worth while. The noise floor is lower yet and the sense of transparency is increased. Bass pitch definition is also improved, and dynamic control on large dynamic swings is better. The subtle shadings or gradations in intensity of a singer, a concerto soloist, a chorus, etc seem to come through with greater clarity and, dare I say it, musical meaning.
System: VPI TNT 3.5/SME V/Benz LP/Luckenk PP1; Ayre CX-7 CDP; FS pre'; Cary SLAM-100 monos in triode mode; Coincident Super Eclipse; Audience Au24 throughout, Silent Source power cords throughout. Arcici rack, two dedicated 20-amp AC lines; FIM outlets; room = 12.5 x 17