KEF LS50 or Harbeth P3ESR for desktop system?

The thing that concerns me with the Kefs is the potential for listening fatigue as they are quite forward sounding.

That's a common misconception. They're not at all forward sounding if positioned as KEF intended: stands no more than 24" tall and zero toe-in. 

@bilitz I listen to the KEF LS50 all day in my home office with a Peachtree Nova 150 class D integrated. I have no fatigue and I am easily susceptible to fatigue from bad sound. I need to acoustically treat my room, because it is small, but any speaker would have been fatiguing without the treatment.

That’s very good to hear. I’m going to give the Harbeths a listen just to satisfy myself that I don’t prefer their sound, otherwise I’d always have doubts. 
I’ll let you know. 
Thanks

On Wed I had some time to kill in Los Angeles so I went to hear some gear I am about to buy, specifically Luxman m900u amp and I was deciding on the c900u amp.

First thing I did was wait for the dealer to finish with another customer. So he gave me the controls to a $16K speaker driven by brand a brand new tube integrated. It sounded good and I am not a tube fan.

When the dealer was free we went to the all Luxman gear and hooked up a $5K Harbeth Anniversary edition speaker that is suitable for a small room (we were in a large room). I was shocked at how the $40K in electronics made the $5K Harbeth sound. It sounded way better to me than the $16K speaker I had just listened too. I played the same tracks on both systems.

So my mind was rather blown and my idea of choosing speakers first before the electronics was changed, especially for my small room. So now I have decided to buy the m900u and c900u and buy whatever speaker will fit into my treated room WITHOUT room correction. The small Harbeth showed me that FOR MY NEEDS the electronics trumped the speaker.

The dealer mentioned that there were a few folks like me that decided to buy the Luxman first and figure out the speakers later. One of his customers uses the KEF LS50 with the $30K amp + preamp. I may do the same since I have a LS50. Though I have some other more expensive speakers in mind. A lot of his customers buy the bigger Harbeth's with Luxman.

The Harbeth was really good with the Luxman but I like the clarity I get with the LS50 a little more. I especially liked how the Harbeth speaker cabinet vibrated with the tunes. Consider me a fan of the Harbeth and it is also not fatiguing.

The KEF ls50s are not forward sounding at all in the modest sized 12X12 room I run them in.

They are however distinctively quite dynamic with a lot of detailed energy through the mid-range. The jump factor is surprisingly good for a speaker their size which I find to be a very positive attribute.