Thinking to upgrade from Audio Research LS27 to LS28

 You could borrow an LS28 from a dealer to compare. But my guess is that it would not be a huge jump. I would say that moving to a used Ref 5se would be a much bigger jump.

 A few years ago I had the chance to buy a dealer demo LS27. I passed because I did not think it was a worthwhile upgrade from what I already had. For fun I borrowed a Ref 5se to try in my system. Tuesday morning came and I was suppose to take the demo back. I called the dealer (who I had known for years) and told him I did not want to return the Ref 5se. I would much rather buy his demo unit. It was so good I did not want to part with it. 

 I am still extremely happy with my the Ref 5se, So much so that I bought a Ref Phono 2se to pair with it. I have no desire to upgrade them. BTW, I have own ARC gear since the late 1980's when I bought a D70 and SP8. So I have own a few pieces.

I had an LS28 and was very impressed.  Then I picked up a REF6 at a good price.  It is better, but not by much (10%?).  Certainly not as much as the price difference.  I suspect the LS28SE has now pulled up to near equal with the REF6.  Email ARC and ask.  LS28's trade used for less than the value I think they are worth.  You potentially could pick up a used one and the get it upgraded to SE when you want to invest more.

what did you decide, pilrem?

I have been all over the place and ended up trading a GSi75 for a REF75SE & LS27.  I know the 75SE is superior to the amp section of the GSi75 and I love the LS27.  I haven't compared another preamp but of course am looking.  I am curious what you tried.