When I had the P-3 I used a stock 12BH7 as the 12AU7 tubes are the important ones sonically. For those I use Mullard CV4003 which are the military version of the 12AU7.
I'm not sure if you are aware but Cary offers an upgrade to the P-3 which involves, among other things, circuit changes that replace the 12AU7 tubes with 6CG7. According to Dennis Had this will take the P-3 to an entirely new level. I believe the cost was $650.
I'm not sure if you are aware but Cary offers an upgrade to the P-3 which involves, among other things, circuit changes that replace the 12AU7 tubes with 6CG7. According to Dennis Had this will take the P-3 to an entirely new level. I believe the cost was $650.