The Gold Lion gold pins I have are new. Really not a huge investment. IIRC about $35~40 per. Yea, you can replace two AX7’s at a time if you wish, but personally, I tried 2 of the stock Mullards and 2 of the Gold Lions, and yea, went with 4. The mix was fine, just didn’t give me the sound I wanted. Don’t get me wrong, the Mullards are pretty good, Kevin D likes them too, but as you, desired more airy sparkle and definition. The Gold Lions are also pretty good bass producers too.
The SBooster is the selectable 15-16.5v model. The Trumpet uses 15v.