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.
RCA Cleartops from the '50s work for me. Andy at VTS has an excellent slection of them. Very low noise.

I also just acquired a pair of Amperex Bugle Boys and am looking forward to hearing the comparison to the RCA.
Amperex 7316 and Telefunken ECC802S are the top 12AU7 tubes you can find.
I agree with S23chang. RCA 5814's and 6189 COMMAND versions should also be considered if you can find them.
But I don't know how easily you will find either of those two tubes, S23chang! If you do, you will pay dearly for them...seriously big money! The Amperex 12AU7's [Bugle Boy] or the Telefunken 12AU7's [ECC 82's...European designation] might be suitable for your rig, Mechans. You might also try RCA's premium 12AU7, the 6189. DO NOT LET ANYONE SELL YOU A "MULLARD" CV4003 FROM THE MID-1980's...these are not NOS tubes, and sound nothing like old Mullards! FYI, the Mullard brand name isn't even printed on the CV4003.

I would suggest that you contact Andy at Vintage Tube Services...he the "go to guy" for all your tube needs, especially expert information.
I had 4 Amperex 7316s sold them on ebay few years ago since I don't need 12AU7 for my application. It shouldn't be hard to find but do expect to pay $100 a pair.
Because of lower noise floor, everything sounds better in every aspects of the regular Holland made Amperex 12AU7 with less forwardness.
Contrary to some views, the CV4003 from the 80's is NOT a bad tube. However, it is system dependent, it will sound hard in many. They should also be low-noise, low microphonic tubes too, like from Upscale Audio (no affiliation). Older Mullards, whether CV4003, M8136, ECC82, etc. are sweeter, with a warmer midrange.

From the 12au7's I have heard, late 50's, early 60's Tungsol 12au7 and a little known Brimar 13D5 are very good value tubes. I also like new issue JJ 12au7's, I think it is a nice tube.

Good luck,
I've liked the Tungsram Industrial grade 12au7 from Hungary (dated 1971) available from A'gon member Tubemonger. Very quiet and detailed.
Thanks for all your input so far. The Mullards I own I bought several years ago on Agon and are labled as 12AU7. I do think they sound pretty good. I am pretty sure though that they are not 1960s Blackburns or anything that old. Probably 1970s possibly 1980s. I have to admit I haven't dug them out to check to see that they don't say 4003 somewhere on them. Any other suggestions? Keep them coming! Once again something that is not overly rare or expensive would be preferred. Thanks again!
You might try the very inexpensive (about 30 a pair) but remarkable jj ecc802's.. great balance between European warmth and American detail. 
I've been doing well with Gold Lion 12AU7s from Cryoset.  Very open, smooth sound and they stay quiet for a l o n g time.

@hifiman5  Do the Gold Lion 12AU7's have good dynamics?   With my Mullard 12AU7's, I can hear the drums but there's no punch.
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