KEF LS50 or Harbeth P3ESR for desktop system?

I have not heard Harbeths, but I have had a pair of LS50s for a few years and have used them in a similar setup on my desk. I agree that they will sound better on stands, but I still enjoyed them on my desk. The great thing about the LS50s is that they will fit whatever space you have (generally). I have used them as nearfield monitors on my desk and on stands in larger rooms and they perform well in either scenario.

I just came across a post on Reddit a few days ago with an impressive setup with a pair of LS50s and a small sub in a large room
http://i.imgur.com/sFJ5BUr.jpg

I have also seen them in a setup much like what you’re describing and generally used with a pair of IsoAcoustics stands
https://i.redd.it/jhhyw0xpbxj01.jpg

I would think these show how versatile the LS50s can be.

I've heard the LS50 and Harbeths and found both to be less alive and airy than ATC SCM7 or SCM11.

I would say Harbeth for tonal accuracy. The KEFs are more metallic sounding. KEF has the advantage of being close to a point source (coherence) and brings more weight to the party in the lower mids and bass.

My vote Harbeth but with the added condition of a REL T5 sub. 

Thanks, everybody!  Bought the Harbeth 40th Anniv. edition.

We'll see if I crank up the existing SVS SB-1000 sub currently on the Spendor s3/5s.  It's all part of the fun.