ARC REF 6 upgraded by ARC.

Another option would be to wait and have your pre updated to Ref7 whenever that happens.

Someone mentioned doing this yourself.

Back in the "very old" days, ARC sent out kits to us dealers for upgrading the SP-3 to an SP-3A1.  I did about a dozen for my customers back then.  I forget exactly--it was 48 years ago--but as I remember it was about 10 parts.  HOWEVER, upgrading to the D-76A amp was a COMPLETE change inside the case, so it had to be done at the factory.

I would guess your Ref6 upgrade needs the factory people to go through it and make sure everything is right.  It is expensive, but if you love the new sound, go for it.  As the saying goes, “The bitterness of poor quality remains long after the sweetness of low price is forgotten.” ― Benjamin Franklin

Cheers!

It's a tube preamp, not that complicated to work on, you probably would get more for your money with a smaller tech like bigkidz.

Ref 6 to SE upgrade is about 5k now excluding New tubes(7).I was not able to send mine back in 2021, so when I called again this month i received return authorization to send in the unit and it was ready to be shipped back ion 2 days.

@tattooedtrackman I mean that the upgrade for 5,000 doesn't seem worth it!  Someone said 18 caps and some wire?  $250 worth of parts? They made a huge profit when you bought the unit new from them . Why not take care of there loyal customers and do the upgrade for a moderate profit.  Do you really think they pay the tech 200 per hour?  Probably pay the tech per unit. But this economy has people raising prices because they can.