I've had a Cornet 2 for about a year now and after rolling a lot of tubes, I've found that RCA NOS tubes are generally the best to my ears.
Right now I'm running an RCA black plate 5814A in the 12AU7 position. I have a couple of RCA long gray plate 12AX7s in the other spots.
Oh, and my Mazda 5Y3GB rectifier is very good, too.