I own that same Allnic amp and love it. We have fairly similar tastes in music and after looking at my options I ordered a pair of Coherent Audio 18's. Frank at Coherent and Gary at True Audiophile have both been great to work with.
I can't say how they sound as they have not yet arrived. They are being custom built to order with some special veneers that Frank found and upgraded internals. They are sending over photos at various stages of the build process and they will look fantastic. They are rated at 102 dB sensitivity and the Allnic should have no issue with those 18 inch drivers (down to 25 Hz and -3dB at 22 Hz). I am hoping they end up being a final purchase, but history tells me otherwise.
I had the same experience as @rsf507 with Harbeth. I tried out two or three models (including the 40.3XD) at my local dealer and never really found them to suit my taste in music even when driven with really nice amplification (Luxman, AR. D'Agostino to name a few).
Good luck and let us know where you wind up!