When I bought my grey shield/plate, early Sixties, Siemens, they were just over $250 a pair(average). My CDP takes six, in it’s analog section. The player’s original cost was just under $5000, so I wasn’t upside down. The diff was remarkable, so- I bought six more, for spares. After about ten years, I thought I might compare the spares to the used. No apparent/appreciable difference
(boy, was I glad!). I’m hoping the CDP will outlive me. You apparently enjoy the clean, wide open, extended sound of the CCa’s. If you’re ever in the market for 6SN7 types, the bottom gettered, 1940’s era, Sylvanias and Ken-Rads, offer the same presentation and are very close to the performance of such as the Tung-Sol round plate, or Sylvania 6SN7W(tall bottle/metal base). Much less expensive than them, too.