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
Ironic that I’m looking for an MA2275 and have ATC SCM40 V2’s to trade. Prety much pairity other than shipping. 

Depending on how far far away you want to sit, they could work. If you want concert levels you’d need the SCM100 or SCM150.  If they don’t sell, I’m looking at either a Pass INT-250 or Marantz PM10 to drive them. Certainly the best I’ve owned. 
bozak concert grands; 1st generation 1957 with16 ohm 8 inch midranges and 4   12-inch woofers; takes 35 watts and it will fill up everything.
Thanks to everyone for providing recommendations and education. I will be able to come back to this post once I am set up for some direction. It has been incredibly helpful. Rich