which 6sn7 tube for my wyetech topaz amp

My favorites were the late 1940's, "3-hole" Sylvania "bad boys", the Sylvania 6SN7W's (not the GTA versions), and the Shuguang Treasure CV-181 versions, if they will work in your unit, and you can find a trouble-free pair.

I'm sure the above mentioned 6SN7 tubes are all outstanding but they may not be so for your amp.
Note the 6SN7 tubes that the Wyetech spec sheet lists is GTA which is not the same as the GT tube.
I suggest you contact the Wyetech to be sure the GT will work with your amp

Bigshutterbug, those Sylvania's you mentioned aren't from the 40's they were only made from 51 to 53.
Those are the ones I recommended in my post above.
Excellent tubes!
Joe

Go to Upscale Audio. They have some Russian 6sn7's from the 1950's. All my friends who have tried these tubes say they transformed their systems
Alan

Vintage Tube Services had wonderful tubes with great advice.