Recommend speakers for a large living room

Pity the audition is in the typical hotel room....

HO, line source speakers sound best in a large uncluttered space, more ’hall’ than ’cluttered’.  Not the typical living room with the usual 'living room accoutrama' .

Lines could work @ the window wall location; @ the circles, feeding into the dining area...*ehh*

*Oooo* Post #666! *L*

"The devil made me do it..."

Oh, BS...I can do fine by myself...*LOL*

With your budget and the amount of space to fill - hands down I would choose either the Sound Lab 845s, 945s or the Maggie 30.7s. Either, when set up properly ( in the location of your red dots would work great - just would have to experiment with distance from the wall behind and toe in) would make a beautiful, well balanced and detailed stage and imaging that would not shift, change, or collapse, regardless of where you are in the room/rooms.  Whether seated or standing anywhere near the sweet zone, either would present a very large, deep stage with pin-point imaging and timber to rival any of the speakers mentioned.
The need for massive amounts of power is a bit over stated. I can't imagine any tolerable sound level that couldn't be (with high quality) attained with a pair of Carver, Crimson/Raven 350 mono, tubes or a quality, high current SS amp.

If a low powered SET amp is your thing, I agree that the super efficient, very nice, open baffle, Spatial Audio X3, would be a great speaker for your large room/rooms. Un-rivaled in performance by anything even close to it's less than $8K price tag - would save you many thousands to put somewhere else. 

Jim
  

gammajo  That's even larger than my former listening room.  Do you think that the 55Ks would be okay in a much smaller room, 15' X 20' X 10' high?  The room is extremely well insulated (16" compound walls/12" 3000 psi reinforced concrete floors-$160K built).  The bass wouldn't be a problem as I am currently using Legacy Focuses with 6 12" woofers but the bass is limited to 25 Hz (okay with me).  I know the Ultra 9s are way too big.

$50k for speakers! Lot to consider, appearances, sound quality, size. Since you mentioned omni directional MBL would be quite the conversation piece and if you trust the reviews they’re always mentioned in Best sound at the show. I have a would be buddy with a room about your size and he’s struggled mightily trying to get music in that room. I can tell you what didn’t work, but for every one I mention someone else will disagree. He is currently using the persona 9h, has a large throw rug over much of the hardwood, but the 20’tall window wall presents challenges. I haven’t been over to hear his latest system, but will soon and can report if interested.