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.