I just sold one of your amps. Really fantastic amp you have there. I liked the Mullard 12AX7 10M as it stood out as a musical never harsh tube that still let all the detail through, with tons of dynamic prowess. I have a big batch of these if you are interested. All the 6N1P's sound about the same to me, so I would stick with the stock tube here.
Upgrading tubes
Recently purchased a new Vincent Audio SV237 integrated and the stock tubes are barely broken in but can’t help but think I can make it better by upgrading the tubes. Currently it has 2 6N1P tubes and 1 12AX7 tube that are chinese manufactured. Any recommendations for upgrading and matching a better set of tubes from different manufacturers?