Made by Klipsch starting in 1958, the legendary Klipschorn speakers haven't changed much at all. But "what are Klipschorn?", you ask?
They are ridiculous. They are awesome. They are huge.
Standing 52" high, 31.25" wide, and 28.5" deep, they are behemoths. They weigh 167 pounds, EACH. They have the shape of a 45-45-90 right triangular prism, and are meant to be tucked into the corners of your rather large listening room. They sell new for about $6000 a pair.
Why this ridiculous size, you ask? Well, Klipschorn eschew the normal cone speaker paradigm and go with a horn speaker based design. Horns are much more efficient than cones, yet have the problem that they must be huge to reproduce anything below upper mids. So Paul Klipsch decided, "Well, shit, let's just build the giant fucker!" (note, not real quote)
The current Klipschorn has this noble driver array (info ripped from the clutches of www.klipsch.com):
Three-way fully horn loaded system using one 1” (2.5cm) phenolic diaphragm compression driver and one 2” (5.08cm) phenolic diaphragm compression driver with an exponential horn and one 15” (38.1cm) fiber-composite cone woofer with a trihedral exponential folded horn.
What I haven't mentioned yet is the simply stunning efficiency figure the Klipschorn put up. Namely, 104 dB @ 1 watt/1 meter (though they don't go the additional step of giving us the frequency they measured this at, this is a pretty reliable figure). This is a good thing. Most cones are lucky to put up figures of 90 dB @ 1W/1M. This means that with the amplifier you already have, the Klipschorn will likely be literally twice as loud, and ten times as powerful. Also given that the Klipschorn have a power handling rating of 100 watts continuous, you can safely crank these things up to 124 dB! (I am not liable for your resultant deafness)
The real beauty of this high efficiency is the ability to be driven by low power but high quality amps, such like the Single Sided Triode amps favored by the nutty Audiophiles.
BTW, they also have a startlingly good frequency response quote, 35 Hz to 17.5 kHz ±3dB. That's some deep bass. Impressive.