What are the best tubes for Audio Research SP-11?

Its all a matter of taste. I owned a SP11 for years (using Threshold solid state amp) and used different tubes for linestage and phono section. I used "GOLD EARO" Yugo Platinums for my linestage and a Brittish 6922 for Phono section. ( sonic frontiers,Parts connection)if my memory serves me right.
I would recommend "Andy" at Vintage Tube Services, or "Kevin" at Upscale Audio. Be prepared to send a few hundred $ if going NOS. The other option is to try a Sovtek 6922,which are new and a more reasonable cost.It all depends on how far you want to go and how much your willing to spend to squeeze out a little more performance. Good Luck.....

HAve you enquired the manufacturer as a start? At least there you will have some tested items as a baseline to do some tube rolling from.

Audio Research is selling the replacement tubes (6) 6922 for $179.00. This is their recommendations.