Klipsch speakers are the easy way out. High sensitivity good dispersion control with the use of horns for the mids and highs, but other wise they are pure distortion generators below150 hz and they don't have the bottom octave of a Mac speaker. The older Klipsch Heritage speakers with the EV tweeter and Atlas midrange driver can't handle the power the new ones can, but have a much smoother HF response. If I were you I would look for some XRT 22 or XRT 30 or the XR290. The 290 gets the nod in this instance. a Pair of 601's or a 602 amp would be a good match for the 290. They'd put put the same or a touch more than a Cornwall, reach an octave lower than either the Cornwall or Korner horn with magnitudes of less distortion. The only current Mac speaker that would really fill your room is the XRT 2K and with the MC 2K amps would set you way back, but would guarantee to impress. Call Audio Classics they had a pre-owned set..
Corn wall maximum out put. 117 db, Korner horn 121 db, XRT 290 , 116 + db, XRT 2k 118+ db. But as the Macs are line arrays they only loose 3 db when each time you double the distance , while the Cornwall is about 4.5 db because of the horn and the korner horn about 3 db too as it is placed in a corner. You realize to get the best illusion for the korner horns they should be placed in the corners on the long wall with a Belle in the center. The focal, point for the Corner horns would be at 15 ft from the wall directly in front of the Belle. If you placed the Korner horns on the short wall the focal point would be at 9 ft from the wall and once you got further than 24 ft from the wall you would be out of the best coverage of the korner horns. Just some thoughts. And remember the Mac speakers will reach down to 16 Hz, where ther Klipsch speakers are rolling off rapidly at 35 Hz. The older Klipsch tweeters can only produce levels with in 10 db of the midrange and woofer. The newer units with the peaky response can reproduce with in 3 to 4 db of the midrange. Where Mac tweeters and line array mids can out perform the woofers in level with lower distortion. Where klipsch mid range and tweeters approach 10 to 20 % distortion Mac speakers are usually below 1% and normally below .3 % for the big line arrays. JBL makes their DD65000, and 66000 with woofers with distortion below 3% like the macs and they can produce the same levels up to a point with as low of distortion as the Macs, but above - 10 db from full output the JBL's start to sag like the Klipsch and the distortion really rises.
So above 110 db the Big Mac speakers have at least a magnitude less distortion than the Klipsch and JBL and in some cases two magnitudes lower distortion. The big JBL's are 4 to 6db more efficient than the Mac speakers at 1 meter, but at your seating location because of the full line array the Macs will be more . JBLs
Now lets get real for a moment. Most folks listen at 85 db with 90 db average for audiophiles and recording engineers. Throw in 10 db for peaks and thats only 100 db, Concert level for live un aided performance is usually 104 db. So in your room at your listening distance we figure you will loose about 6 to 8 db. So you add all that up and your speakers would need to be able to produce 112 db. Well the kipsch horn would only need 6 watts. Corn walls 14 or 15 watts and the Mac speakers about 200 watts. Not really a problem. But then you throw in the impress factor.
My speakers are 95.5 db at 1 meter 2 watts, so all I would need for 112 db is 80 watts. I have the potential for 720 watts for each speaker. I have never seen a power guard light flash or a meter go over 100 watts. And I'll guarantee the level was loud enough to impress.