Anyone have experience comparing NOS GE vs RCA 6L6?
truth depends on your vendor, your gear and your ear..i have a mix of new and nos. My 6L6 in a very heavily modified MC240 are Sylvania….but like @noromance i have an open mind….and ear….

I get tubes from only a few places, very reputable..Andy at Vintage tubes and RAM.

best to you on your musical journey 
I agree that new production tubes are getting better, but old stock tubes still sound better in my experience. This is particularly true of preamp tubes.
Thanks for all the insight.
So what tube type would add some weight or substance to the music?