Congratulations on the upgrade!
My friend, with Lamm M2.2s, and myself, with Lamm M2.1s, have also been using the Amperex pinched waist 6922 tubes for several years to good effect. However, I will state that other NOS tubes can sound very close to the pinched waist tubes sound. (Such as the Amperex Orange Globe 6DJ8 tubes, and they cost only a fraction of the cost of the pinched waist tubes. However, I agree that for the ultimate in sonics, the pinched waist tubes work the best, IMHO. And you are most certainly correct that replacing the stock Sovtek tubes is a priority to getting the best sound possible out of the hybrid Lamm amps.
My two cents worth.
My friend, with Lamm M2.2s, and myself, with Lamm M2.1s, have also been using the Amperex pinched waist 6922 tubes for several years to good effect. However, I will state that other NOS tubes can sound very close to the pinched waist tubes sound. (Such as the Amperex Orange Globe 6DJ8 tubes, and they cost only a fraction of the cost of the pinched waist tubes. However, I agree that for the ultimate in sonics, the pinched waist tubes work the best, IMHO. And you are most certainly correct that replacing the stock Sovtek tubes is a priority to getting the best sound possible out of the hybrid Lamm amps.
My two cents worth.