Can you tell me why I didn't like the Reference 3a MM's?

So I recently asked about a new amp on the Amplifier forum.  I got a lot of good advice and ended up with a Pass XA25.  I really like this amp and the sound.  I have been told by Reno Hi Fi, Pass Labs and B&W, all of whom I contacted, that the XA25 is under-powered for my B&W 705S2 speakers.  But it sounds very good.  However a little flat when the volume is low.

So I am looking for some more efficient speakers.  I tried a used set of Reference 3a deCapo MM's, but they did not have the clarity of the B&W's and sounded a bit muddy at times.

I am looking at Omega Super Alnico HO's.  But I am wondering if the full range driver sound is what I didn't like.  

Am I wrong in thinking more efficient speakers will sound somewhat better at a lower volume?  Can you possibly tell my why I didn't like the MM's?  Something about their design or build?

Any thoughts on the Super Alnico HO's?  I don't want to move down the speaker sound chain.

Thanks much!  Any other speaker suggestions welcome!  But not horns.  I am not a Klipsch fan.