@thecarpathian Yes was an interesting read. Thanks.
I spent some time on the Brent Jessee website. Read the review of the Pharaoh II.
Been running my Sphinx Ii for several hours. Seems to be sounding better as hours go by. Going to let it break in. Get adjusted to how is sounds. Room is rather barren at the moment, still needs window shades and more furniture.
Have yet not called Mark O'Brian of Rogue Audio. I intend to do so.
I hope not to spend more than ~$200 on a pair of tubes.
Thanks to all contributors!
Not a Sphinx, but FWIW when I had a Rogue RP7 (driving a ST100 I still have), my favorite 12AU7 type in the primary position was the venerable Amperex 7316. It was the most dynamic, holographic, with just the right amount of "sparkle". The Amperex 7316 is difficult to find these days and commands quite the price. For a "fatter" sound, but still plenty of top end air and a wide bandwidth, RCA black plates did very well. These tubes were sourced from Brent Jesse. I tried many 12AU7 combinations and spent entirely too much money doing so, but I learned a lot and it was fun. Honorable mentions go to the Ken Rad 12AU7, which is a very unique and beautiful, almost chimey (in a good way) tube. I did not like, and TBH have never liked Mullards in my equipment.
$200 is a very good budget. Brent is a good guy, so that is great if you buy from him.
I recommend the RCA 3 MICA Black plate 5814A tubes from the 1950's. Nice warmth and bloom - good transparency and dynamics...maybe $77 a pair. Also, the CBS 5814A - less warmth, better extension on top and bottom, great transparency. Raytheon is also excellent and similar to the CBSA.