I just swapped the Merlins for the Unifields again. Maybe there is no best. Merlins are more detailed/analytical and the Unifields are a bit more cohesive, have more bass extension and are a bit more laid back. There is a little more action at low volumes with the Unifields as well (and they are a bit more efficient). Let us know what you end up hearing.
My Merlin's don't sound dead. What version did you listen to? Maybe it was associated equipment.
The Harbeths are a great size for the desktop, unlike the Theils. I had the p3es2 not the 'r' version but the bass was not acceptable to me with my MC275. With a more powerful SS amp it was though. Oskar recommends at least 50wpc so I'm not sure the op will have the wheats for them.
I've not found a rear ported speaker that works on my desk but I am up against a wall. Some1x, what is your desk set up like?
I've been on the hunt for the same. Have Merlin TSM-MXE, Von Schweikert Unifield One, and 47 labs 4722 here now. All three are different and all are good in their own way. If I had to choose a best today, it would probably be the Unifields. They are each in a separate price category though, so what is the best value? I don't know.
What amp are you using?