Speakers for a very large room?


Reader of posts for a few years but have not posted a serious question until now. Currently have McIntosh integrated tube amp with some old KEF speakers. While I enjoy it in my current setting, I am moving to a house where my listening room will be 30' x 40' x 10'. It has polished concrete floors. Sounds like a grocery store but it is not. I suspect I will need to change speakers but really have no clue where to start. I listen mostly to progressive rock but also anything in the same general area. I don't know where to start with such a room? I am at least 3 hours from any major city. I did experience Treo CTs once and to bright for my ears and Wilsons but did not care for the visual appearance though liked the sound better. It was a few years ago so can't better define what I liked.  Not a great resume of listening experience but it is what it is at this point. For some reason, which may be completely wrong, I am thinking electrostatic may work well in this setting. I could easily move them 5 feet out from the back wall but then again I really don't know what I am talking about. Any kind comments would be appreciated.

Rich
ricmci
Ok. I have to admit that I am one of those loyal McIntosh customers but would be willing to eventually upgrade in-brand.  They have treated me well over the years and I love the warmth with the kind of music I like. Might be short sighted but it is what it is.  Anyways, I am hearing room treatments and klipshorns with subs over and over. Much appreciated. I will start there. The one thing I love about this hobby/addiction is the ability to not do things hastily. Sit back and reassess. If you think you missed a good deal, it will eventually come around again.  Thanks to everyone for your insight!
I have a similar sized listening area. A bit shorter and smaller at 36'x24'x8 with concrete floor.

I am using Canto Ergo 1002DCs. No sub. The front ported speakers are 20" off the wall and 108 " apart and I sit 96" back from the line connecting their faces. I've done absolutely no acoustic treatment other than moving furniture. All of the surfaces in the area except the floor are broken up by furniture, cabinets, etc. The Ceiling is irregular, too. I've tried with and without carpet and I prefer without. I did take a lot of time adjusting the position of the speakers with the aid of a CD created for that purpose. I really like the sound of my system, so I suggest you set up yours and play with it before you decide what to do next. It's a little weird sitting in the middle of the room, but I pretty much have the space to myself, so who cares how it looks.

Happy listening
Another vote for a sub woofer (I failed to mention earlier) with the Khorns. You would think those massive speakers with 15" woofers would produce deep base, but they really don't. I had 1 sub, but I read a lot here that say 2 are better. Might be more so with your room that is huge.
 
I am in the same boat- new home being built will have a great room 42' x 25' with 14' ceilings and polished concrete. But it gets worse-one long wall is all glass. I have a pair of GE Triton 1's from my prior home that were amazing in a smaller room with full GIK treatments using REW. My plan is to use the Triton's on the short wall with a sofa/chair about 10' away in the sweet spot. The issue isn't to fill the room as much as to fill the listening area well enough. I plan on 2 additional subs to help achieve that. I will use large area rugs but I also expect that I'll need Dirac too with so many reflective surfaces. If my concern was to fill the space, I'd go with big constant directivity horns. The frequency response stays the same off axis, and if they are big enough, you get good sound without being in the typical sweet spot. The prior JBL synthesis suggestion is a good one though I still think you'll need additional sub's. I also second the Tektons.