Speakers for a Large Room (20’x37’)

I would look at the Vivid Kaya line.  I have recently heard them in a large listening space and was very pleasantly surpirsed despite the relatively diminutive size of the Kaya 45.  There are similarities between the Kef Blades and the Vivids in terms of cabinet as they are both fiberglass though I like Vivids core better.  They both have side firing woofers in opposition, etc...

The actual baffle size is less critical.  It comes down to the amount of energy that exits the cabinet and the Vivids and Kef do a wonderful job of daming internal sounds so that most of the energy exits the cabinet.  

Horns of course do the same.  IMO, you get a more lifelike and refined sound with the Vivids or the Kefs but they are quite a bit more expensive.  

Audiotroy's point has come up before.  Years ago over in Stereophile forum, I had made a comment on the LS50s and he argued they had an issue at high volumes due to the tweeter limiting excursion.  This would extend to any speaker using the UniQ driver and even showed it in a measurement plot they provided.

I am not a Kef dealer or expert and can't speak to it.  Only that I have heard it raised as an issue previously.  I will tell you that Vivids will not have this problem.  And, even though you would think it would be an issue, near wall placement with those side firing woofers is not an issue.  I have tested it on my Kaya 45s.  I am not sure how or why it works, it just does.  
 

@yyzsantabarbara that is consistent with my experience.  Usually, you only run into an issue if the cieling is low (like 7' in a basement) with a bigger speaker like the K90 or a G2.  Front and side walls surprisingly have minimal impact.  Even the rear firing oval decades work well in a customers home and he had one basically in a corner.  It is really amazing.