@bluethinker Marcus, I received your message, but I can't reply, so I dug up an old post. I don't have payment information and a phone number on file with Audiogon, so I can't send messages.
I have a couple of output tubes (using Sylvania bad boy 12SN7GT), but the input tubes seem to make the most difference.
My favorites are Telefunken Diamond Bottom ECC801S. A close second are Siemens ECC801S (German made in 60's or early 70s). I could happily live with these. They have just slightly less detail than the Telefunken.
I have also used Brimar 6060 Yellow T (CV4024). If you want a warmer tube with slightly rolled off highs, they sound great. Tried some JAN-Philips 12AT7WC because they were cheap. They actually weren't too bad, but I didn't use them. The preamp shipped with some Trigon 12AT7 that were actually my least favorites.