Cary 805B Question

I thought one of my monos needed repair, but it turns out one of the 300b tubes went south.

I swapped in an inexpensive pair of tubes and decided I need to get a new pair, and possibly a new pair of 211 tubes, as well.

My 805s use a 6SN7, 300B and 211.  Of the three tubes (one, two and three looking at the amp from front to rear) which contributes the most to the sound quality?  
 

Thank you.