Small or big tubes/valves for pre amp ?

@steakster brings up a notion that I didn't think about; auditioning some preamps. We've only been referring to 6SN7's and the Sachs preamp, but there's a world of tube preamps out there. Many fine 12AU7/ ECC82 based designs in which equivalents can be rolled-in. There are so many premium NOS tubes available that take a AU7 design to a higher level. I've used 5963, 5814A, 7316, CV4003, CV491.

With that said, I love the 6SN7. IME, no other tube sounds like it. I'm on my second preamp based around it and no matter what the design, it sounds heavenly. 

I think this is very close to my observations here
https://www.audioasylum.com/messages/tubes/221750/6f8g-vt99-observations

The 6SN7 Tung Sol and the Ken Rads , that Andy had, at least one of the tube in the pair , was somewhat .
microphonic in my system. If you can find those that are not microphonic, the Ken Rads and the Tung Sol are the 2 brands that actually have Bass that I can live with , most all of the other 6SN7s do not ...IMO
This is what they look like .. this is not my  amp . Scroll down a little bit 
https://www.head-fi.org/threads/wa22-lets-roll-some-tubes-done-mod-burnning-in.451678/page-27

Thanks for all your inputs, really appreciate it.
I live in a far remote area so no chance to listen to other gear, with a pre amp that uses tubes it would give me more chance to tailor the sound for my preference, my speakers are bbc speakers, so easy to amplify, they are 8ohm and don’t go below 6ohm, but they are very revealing in tone and timbre, tone, timbre and space I find tube do better than solid state, and by changing the tubes I can get closer to my sound ideal.
For power amp I had planned to buy a Belles sa100 that I can get at half price (demo) but have also heard very good things about the Van Alstine set400, will see what I end up with, wish there was a solid state pre that sounded like tube ))) then no need for replacing tubes;-)

@grey9hound - I’ve been using 1940s, Tung-Sol(round plate/JAN CTL/VT-231) and Sylvania (6SN7W/JAN CHS/tall bottle/metal base) tubes, in my monoblocks for a couple decades(one each per amp). I’ve kept a stash of bottom-gettered, 1940s, Ken-Rads and Sylvanias, for back-up. They were specifically chosen, after listening to every one of the the top fifteen tubes mentioned on the following list, for their low noise/microphonics and lack of excess warmth/sugary glaze. Regarding Sylvania 6SN7s and Bass: that’s EXACTLY for what the tall bottle, metal-based Sylvania 6SN7Ws are known(slam). I’ve found all the(early) Sylvanias, well balanced from top to bottom, except for the short bottle 6SN7W, which(to me) was unlistenable. (http://www.dehavillandhifi.com/6sn7_vt.htm)

Andy even said the Sylvanias don’t do bass. I do not know about the metal base 6SN7W. They are as Rare as Hen’s Teeth
Try taking out the Ken Rads or Tung sols and run just the Sylvania in both spots if you are talking about running both Sylvanias in V1 and V2, I’ll bet your bass will suffer .I know Ihave  tried a lot of different Sylvania 6SN7 and could never find one that had great bass
If the Metal base 6SN7w have good bass , then they would be the only Sylvania 6SN7s that do.IMO
Do your amps use one or two 6SN7 tubes ? I am confused about that