Tube recommendations

@infection , Brimars are not as warm as Mullards, that's why I like them. What makes Mullards so special is that adding a premium NOS can make music sound holographic when combined with the right set of tubes. (these are the expensive Mullards).

Brimars have VG high and low-end extension, very natural sounding. I think they are best when used in the preamp line stage or as input tubes in an amp.
These added some warmth to my system without rolling off the highs...
https://www.upscaleaudio.com/collections/preamp-tubes/products/brimar-cv4003-12au7

The 12AX7 Brimar goes for about $120 to $150 each. But the best is a CV military type for about $150.

A problem with tubes is that you can not stop trying different tubes when you're realizing how good those vintage tubes are. It's an addiction. So don't expect that you will buy the right tube, you will buy many of them and they are different from each other, they are all expensive.