Tube upgrade for Unison Research unico

I just bought some cv4003 from upscale audio.
i hate to hear they are suspected of selling fake NOS Mullard cv4003 tubes. I'll give MTS a call and reply back on the tube comparison. 

I've used NOS Brimar 13D5 and CBS/Hytron 5814A and enjoyed the sound, but they're expensive and were not long lasting. I've found the reissue Tung-Sol 12AU7W/6189 tubes from Cryoset sound good, are affordable, and last a long time.

I have had (and continue to own) a Unison Unico which I purchased on Audiogone in 2010.  I have tried a number of 12au7 tubes from Upscale and other sources.  The ones I have tried:

1. Radiotechnique 12au7 - came with the unit and does not sound good at all.  Not sure of the condition of the tubes when I got them, but were only used for a few days and now they gather dust.
2.  RCA Cleartop 12au7
3.  Mullard CV 4003
4.  Seimens E82CC/12au7

Among these, the Seimens is the clear winner - beautiful midrange, a great low end, clear, airy highs, and fantastic dynamics!.  From low to high they are the best.  I like these so much I bought a 2nd pair as backup.

I got the Mullards after reading their praises and thinking - 'if these are better than the Seimens this will be amazing'. The Mullards have a very nice midrange as well - comparable with the Seimans, but the upper end in comparison seems a bit soft and not as extended, while the bottom end seems to be missing some extension and 'fullness,' for lack of a better term.

At the same time I got a pair of the RCA cleartop.  This is a nice tube, but definitely a step down from the Seimens. Slightly better upper end than the Mullards but not as good in the midrange; bottom ends comparable.

To my ears, Seimens-Unico is a match made in heaven!

Enjoy your new amp -  this is an underappreciated gem.