Tube choices are very subjective depending on your total system and musical tastes. My experience with trying 12au7s. I have tried Mullards, Telefunkens, Amperex, GE 5 Star and RCA Cleartops. My system is SS amp (Plinius) and ProAc Response 2.5s. I have settled on the RCAs for their pure musical nature as well as value. I have found the Mullards to be too laid back, the Teles a bit forward. I like the Amperex, but at twice the price of the RCAs, they're hard to justify. So, it would seem to reason that the sonic signatures of all these would be similar. I do agree with the comments made regarding Andy Bowman. However, he is very pricey on his products, albeit very selective and honest. If you're ready to drop $40-$50 per tube, he can't be beat.