What are the best drop in subs for a 12AU7??


I am considering a Minimax preamp, but understand that they sound best with rolled 12AU7s. I have some Mullards which I would try first but have heard that there are even better choices of slightly different tubes. What are they and are they difficult to find? Thanks any help is appreciated.
mechans
Post removed 
The dynamics are excellent across the frequency range. Kick drum is kick ass.  I tried many different tubes including the Mullards but they got noisy fast.  I would agree with you that they lacked PRAT that gets the foot tapping.  I buy matched pairs from Cryoset.  The current pair has close to two years on them and they sound great and are still quiet.  Frankly, I purchased another matched pair several months ago so I would not have to go without my system if a tube failed.  Those new tubes are still in the plastic wrap!

What are the best drop in subs for a 12AU7??
NOS RCA black plate 12AY7
I found these to be best for input tubes, not too soft/rounded as 12au7 and not to highlighted as 12AX7.

Cheers George