Speakers for a Large Room (20’x37’)

@jackd  Hadn't really considered a boxless speaker.  Are there advantages over other types of speakers in a larger room?

With a large space and using the long axis I would consider something like Wilson that can generate a good sense of power. Generally a Wilson speaker will require big amp output. Stand Mount could work as well. A good quality speaker makes all the difference in sound. BTW a baffle will add a bit ( 6db ) to the power response of a loudspeaker.

@doni 

More forgiving of placement and the Spatial's use professional drivers are capable of effortless high volume.  With the X series you have the choice ot 2 models with the powered bass driver or a recently released all passive version. I have a pair of their all passive predecessor that I use in a room similar to yours at 22' x 26 x 10' for the main part of the Family Room with an 8' foot wide opening into a 14" wide Kitchen/Breakfast Room.  They can fill the whole space effortlessly at almost unbearable volumes if that's what you want.  They are also very effiecient at 97db for the power models and 93 db for the passive. Another speaker that has worked well for me in that environment are the Nola KO's whose upper half of the cabinet is open baffle with the two woofers in a ported enclosure at 91db.  I think at the current price the Nola is about twice as expensive as the Spatial.  If you want more info on the Spatial look at their dedicated area over at AudioCircle.  Many dozens of happy owners and participation from the company owner too.

If you can wait until next summer, and it's in the budget, the new Klipsch Jubilee. I have heard the Jubilee and the new Cornwalls. At low levels, the Jubilees still project so much power, it's unreal. They are effortless.

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.