My favorite 12AU7 is the 7316 Amperex which is a drop in sub. They were an early "computer" tube made only at the Heerlen Dutch Phillips factory in the late 50's to mid 60's. They are often labeled as H/P etc. They are a very extended, crystalline, halographic and transparent tube. For 12AX7s it really comes down to some compromise. I don't know a "do it all tube" but my favorite is the well loved Sylvania triple mica blackplate 5751, which has most of what you want. The GE 50s TMBP 5751 has more pronounced bass. A low noise all roud clean and clear sound may be best found in the rare windmill getter mid 60s Ratheon 5751, as well as the Telefunken 12AX7 as suggested above
