An ARC preamp seems like the logical choice. If I was going to have one ARC piece it would be a preamp. I have not heard the LS26. I spent a week or so with the LS27 when I was thinking of upgrading my LS25 mk2. I thought it was a sideways move. And in some ways preferred my LS25 mk2. I would look at one of the ARC Ref preamps, a Ref 3 or ultimately a Ref 5se. The Ref 5se is in a completely different league than the LS27. And the Ref 110 with the Ref 5se is a spectacular combination.
I have not heard the ModWright 36.5. Most of their dealers are in the pacific northwest. I wouldn't mind hearing one. But with only one balanced input, it would not be a good fit in my system.