Klipschorn-Klipsch-The Loft NYC

There are many at the Klipsch Speaker Forum who may be interested in your question.

You need 4 K-horns easy enough to buy used just can't ship them too easily or just buy them new and they will ship them to you. I told you in the other thread that Mac amps would be a good match!

perfectly square room will suck no matter what speaker you use, or where you place them. Standing waves will eat your lunch.

Maybe if the place is full of soft bodies (people) it will work out OK.

Two Khorns and about 20 watts will make everyone in there go deaf. But with smiles on their faces.

Is this a dance studio, a dance club? Are you gonna serve drinks? K-horns will sound awful in a large, hard surfaced room unless you get (as you stated) tube amps and the room gets full of people. Bodies make excellent sound absorbers and diffusers.

I was just reading an exerpt from Love Saves the Day: A History of American Dance Music Culture, 1970-1979 by Tim Lawrence. Mancusco used both Klipshorns and La Scalas in his club. You can regularly find La Scalas for 500 - 600 dollars on ebay, sans shipping. The bass is not as deep as the K-horn, but for modern music, you will have to augment the bass anyway. Finding an appropriately fast, high output subwoofer will be challenging. If money is not an issue, Avante-Garde makes a horn subwoofer. They do look cool, so I guess you could justify the expense becuase of the wow factor. They could be prohibitively large for your venue. While on Avante-Garde, their main horn speakers are highly regarded in audiophile circles. Keeping them safe and yet visible so the MOMA design can be admired could be problematic. Shahanian Acoustics made a large horn subwoofer called the Contra-bombarde whose form factor is friendlier, but I have only ever seen one for sale. There is a pro grade servo driven sub made by ServoDrive inc. They have two models, a compact bass reflex (ContrBass) that goes down to 18hz, and a horn model (ServorDrive BassTech 7) that goes down to 28hz. Given the small space the bass reflex model probably fits your need, though it is not as efficient as the K-horns. You may even be able to arrange getting one to audition in your space. VMPS makes "The Larger Subwoofer" that has similar specs to the ContraBass, and is under $1K, though may not be as bulletproof.