AS far as rear loaded horns go, i have a pair of Klipschorns, which are nice. But i will tell you...placement is a problem, as is imaging, etc. One thing i have been thinking about after reading scotts's review is an active crossover and bi-amping, with a 15 inch high eff driver in a 4th order box. I have a pair of EVforce 15s lying around that are 100 db eff. The curve looks real flat in the bass region, down to about 25 Hz! The Khorns, which are cool, only go down to about 35 HZ. My guess (not having heard actively crossed subs, i can only base it on other people's reviews) is that an actively crossed biamped system, with a sub, a fullrange driver and a super tweeter will sound better than a corner loaded horn....but the proof of the pudding will be in a hear-off.

I know you are a solid state man, and yet you were blown away by the clarity of the lowthers. I think at this point, i would URGE (challenge ;-)) you, if you have not already, to try a good tube amp with your lowthers and see if that does not make a difference!
-akhilesh