12x7 tubes

I agree with Joe's Tube Lore that the USA - made 5751 is the best bang-for-buck choice!

Except it has 70% of the gain.

5751

Trying to match the right tubes with my system that  consist of a music fidelity m6si and dynaudio special forty’s speakers.

Brent Jessee is a great source ,

Tubemonger is another one ,  I replaced 3 RCA black plate 5751's 

with " slovakian " 12ax7's ( ecc803s ) in my phono preamp , Love Them .

The gain of a 5751 is 70% of a 12ax7 but you don't hear 70% less ,

the difference is about 1.5 dbs or a notch on you volume control .

I always buy my tubes through Brent Jessee - the tubes he recommends have always been a good upgrade to my gear...  Just got one a few weeks ago, in fact.