The Lamhorn is very good - can be forward.
The Beauhorn is also very good, quite a bit smoother, but less heft.
Of course neither of these have any real highs (and if you 'throw in a super-tweeter' you're now building your own speaker).
Devore are great speakers but they are really not high-eff in any sense, though they will play on a 300B.
Klipsch can sound decent but the people who say they are mid-fi speakers stock do have a point.
The various Fostex backloaded horns have beguiling qualities but I have not heard one that did not have some forwardness/peakiness issues.
The Audio Note AN/Es are very special and will play decently on a 45 SET. Unfortunately in a great many rooms it is nearly impossible to get smooth bass in the corners and out of the corners the bass reach is quite compromised.
The Tonian speakers are absolute, pure genius.
