Yes. Audio Research dedicated a person to upgrades, so the turn around time dropped very significantly.
I upgraded from a Ref 5SE to a Ref 6SE… so I can’t comment on the 6–> 6SE specifically. But, I am sure you will enjoy it. I have had the REF 3 and REF 3SE Phonostage in my system, and can attest to the upgrade being worth it. From experiences of others on the preamp upgrade, I think you will be very happy.