I have a pair of HLM Mk 1's ( Grand-daddy of the SHL5) I am a hardcore ESL accolyte - the only reason I don't own any is space. The Harbies are in my experience the closest a box can get to the ESL musicality, detail and transparency, and I have played with some high end boxes.
Contrary to popular myrh, Harbeths are easy to drive and unfussy speakers. Having said that, the bigger ones do shine better with more amplification headroom. What Baggawire's Modwright did with mine at a recent bake-off convinced me to go seperate pre/power, and I'm now looking at dual-mono amps.
Personally, I'd go as high up the range as you are comfrtable spending. For you I'd say the 7ES-3 would be the entry point for your set-up and music choices. The P3ESR's are beautiful, but may not quite deliver the low end extension I imagine you'd want at quieter volumes .
Have you seen these?
I love my Harbeths.
And I'd avoid any dealer that wants you to spend so much money with no home audition. I used to home-demo speakers twice as big and half the price for prospective clients back in the day.