Gwalt,
Congratulations on your BP upgrade!
As an owner of a BorderPatrol P-21, I can attest to the strength Gar's power supply add to the guts and delicacy of the amp.
I've also asked this question to Dmarkov so I'll repeat my question.
I was running Sophia Carbon Princess which I loved for their rich, yet detailed and dimensional presentation. However, I ended up having to return my amp to Gary for repair after an issue with the tubes. Evidently they are not compatible. I replaced them with Electro Harmonix which are fine but don't have the magic. Knowing the P-21 is a push/pull, I'm not educated enough to know if this configuration is harder on tubes.
Any suggestions for an alternative to the EH?