best for 6sl7 and 6sn7 tube nos?

i have northren electric 6sl7 , i need also invite 6sn7 3pcs , what you think is the best preamp in both entrey 6sn7 & 6sl7 
tnx you foxes
My Integrated Preamp/Amp uses a pair of 6sl7 and 6sn7. 1st time I ever had these types. Cayin A88T. I love it's sound.

Which specific tubes?

Factory tubes sounded great (no identification of tube maker).

I blew one (put in wrong socket). I put a spare GE I had in a drawer, sounded great. Then bought a new matched pair, they sounded bad. Switched them for a different brand, half the price, they sound wonderful just like the original's.
There is no best, and the arguments about these types are endless and can be found elsewhere on the internet. Again, check Tubes Asylum to start.
I am a believer in NOS tubes, but I don't have experience with those.  Call Brent Jessee or Andy Bouwman of Vintage Tube Services and they'll help you get the right tubes.
Andy at Vintage Tube Services is my go 2 expert…..and he has killer test gear….
Andy at Vintage Tube Services is my go 2 expert…..and he has killer test gear…
+1 @lewm

good thing about 6sn7 and sl7 is there are many many makes and types, old and new, from many different places over the world, all with their own sound - but most sound quite good, some really excellent

lots of choices, tube roller’s paradise!
When I needed some very quiet 6sl7 tubes for a phono preamp Andy at Vintage Tube Services recommended Sylvania.  He set me up with a NOS pair that were excellent.  I sold the phono pre shortly after I received the tubes as I acquired a different pre with phono built in but still have those tubes.  Also have the RCA 5691 red base tubes.  Sylvania a little more air while the RCA had a little more meat on the bones…