Best sounding tube for Audible Illusions M3A preamp?

I am interest in learning what folks are using as the best tube for preamps, specifically, the Audible Illusions Modulus 3A. (My AI M3A also has a Gold phono stage card, but that is purely solid state). I have reviewed nearly all the tube roller-specific forum threads here, which are spread over  several topic areas. I have also reviewed another thread located elsewhere ( I know that AI recommends the 6H23n tube for the M3A. So please let me know your thoughts about this tube and whether you can recommend a particular brand of the tube and commercial online supplier. I would also appreciate your view of alternative tubes (including brands and online suppliers), should you recommend something other than a 6H23n tube for the AI M3A.
6H23NEB tube.  Any others will last 6 months or so.  Trust me I learned from experience.  I had an original Modulus 3, 3A and 3B.
ECC88, PCC88 - Tesla, Siemens, that sound better. I use it in my DIY projects with SEs 300B, 2A3 Loftin White, 6P31S, 6P13S, 4P1L EL84, EL83, EL11....
6h23eb is super rugged....   have had one in my c-j which can be tough on 6922 type.   The new Gold Lion 6922 is durable too , have one in my Classic 2 SE and it's at least 2 years old and still sounds great and zero noise.   
You have not choice than 6H23EB.  Sounds beautiful with M3A and last much more than other brands. I have tested many and use Reflektor for many years now.  Look them in and buy in matched quartets.
The Audible Illusions M3A runs it’s tubes very hard, probably why they sound so good, buy in bulk whatever you get.
My friend changes his every year with 3hr or so every night listening, and he hears the difference with the new ones every time with the same ones, from "New Sensor" he bought in bulk lot got them cheaper.

Cheers George

I've had my 3A since they came out, and Telefunken sounds good, and they have lasted.
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Accidentally found this old thread and I want to share my experience with AI Modulus.
My preamp keeps tubes warmed up in stand by mode, so I always unplug it when I don't use it and it obviously extends tube life. I plug it in 5 min before use and it sounds amazing.