5 responses Add your response
These links are informative and should be helpful,
Personally, I don't have any experience comparing different 12AU7's.
As a Cary dealer, I feel that the 03 is very good preamp in stock form(especially at it's current price point). However, it will really come alive with a little tube rolling.
I've had great luck with Mullards and RCA's. Do a quick little search online and you should be able to find several different great options depending on what type of sound you would like to end up with.