I'm going back and forth between the three RCA tubes now. If only I could have the smoothness of the Black plate with the taught bass and midrange warmth of the 12aV7... Kills me.
I read somewhere in this thread that a user was unable to tell the difference between extremely expensive tubes and the cheapest cheap ones that they had. Sometimes I worry that there isn't much difference and that it's all in my head. I may run the output back into my computer to run some tests... wonder how I'd go about that.
Dont worry, its what you think is right is the best choice. Pick the tube you like and that sounds best to your ears. Audio is a highly subjective hobby and some like gear others dont like at all. Its like picking a Hotel or B&B that has good revievs on Tripadvisor but when you get there you have different preferences whats important to you and you might like it less. The other thing is that Audio is not just about the sound but also the perception of the gear (looks, functions etc).
My Mullard 1955 for example, I just did not buy that because i thought it sounds good (or has a distinct sound signature) but also because I like old things and I just thought it would be nice have somthing like this very rare tube. The sound is not 10 times better than a normal 10$ tube but i can clearly tell the difference between a J&J and the Mullard. And some 5$ tube might even sound better to your ears, who knows...