I've heard a lot of BLH cabinets and the Lamhorn cab has been the best by far. Usually the BLH design the horn bass output seems separate, out of focus and lagging behind the rest of the music, the Lamhorns are the only BLH I've heard that sounds well integrated. Also, the AERs likely have a more even frequency response vs the Lowthers, but I am guessing based on hearing both... Lowther had a peak in the high treble around 7 kHz which is responsible for "Lowther Shout" and AER did not. Lowther drivers can sound good at first and later be fatiguing. Some people love them, but if you are not familiar with the Lowther sound you are taking a big risk with them imo.
You need to consider whether a BLH is the right choice for your room, they may have too much bass output for a small room and it may be the case that a simple bass reflex cabinet would suit your room better, I can also say that the Omega single drivers are certainly in the same league as any other single driver in the world regardless of price and the cabinet designs may suit your room better, the only issue is it would be nice to have 6 dB better sensitivity for your amp... but this won't matter at all if you don't listen at high SPLs.