The target is to achieve better sound. While I have not taken delivery of the units yet, it is always good to plan ahead due to long lead times nowadays. If, there isno benefit to change to NOS tubes, then I would have saved some money. If there is a benefit, then it is money well spent. Prior...
Actually, I asked my dealer to check with factory. Factory reply was that any other tubes other than the ones originally installled would need to adjust gain and L,R balance. Being the anal retentive person that I am, I can't help but to seek opnions from fellow users.