@erik_szilagyi , try asking your question in this thread: TUBES(pre, power, rectifier)
There are a few Pendant and ampsandsound owners discussing tubes they recently bought. You might want to add a bit more information about which tubes you currently have, e.g. are they all stock JJ tubes?
Also, be aware that the name “Mullard” has been bought, and the new production Mullard tubes don’t sound anything like the originals, so you will need to be careful about checking whether or not they are NOS. For instance, all the cheap Mullard tubes in your link look like new production to me. On the other hand, NOS Mullard can get very expensive.
I’m personally looking into switching out the 12au7 tube in my Pendant (currently a NOS Sylvania-manufactured Baldwin, provided by Zach) but unlike you, I don’t want to go warmer, so from reviews I’ve read, I’m avoiding Mullard and Brimar right now.