This is my take on the Klipsch speakers.
Sarah Knight's definition is spot-on with the "Power, Detail, and Emotion". Also, I found the Klipsch to be very Dynamic in thier musical presentation, especially when paired with a good amplifier. I found the dynamics and clarity to be unbelievable in my RF-7s driven by a B&K amp. For example, I've listened to other makes and models of speakers, such as the Martin Logan, but the thing that really struck me was how well the percussion (i.e., drums) came out of the Klipsch. Also, the vocals were extremely clear and legible on the Klipsch as well. By "detail", that means how you could hear every little nuance in a performance. One of my friends told me that he has never heard anthing so clean and detailed as on my own setup. He could not believe how easy it was to pickout and hear each individual instrument. Your "precision" and "poised" also seem to fit very nicely as well. These speakers do have a very precise feel to them when listening to the music as well.
The Effeciency angle is definity a hallmark of Klipsch design, especially in the larger models. Just take a cruise through the "two-channel" section of this forum, and you'll see just how many of those guys up there are listening with tube gear that provides maybe 20 watts max in most typical cases. I've heard some of those setups, and they do indeed sound incredible, even with the power/progressive metal that I typically like to listen to on my own setup. Also, the Klipsch are very inexpensive for what you are getting! You can buy quite a bit of speaker for a relatively small amount of money, compared to many of the other high-end brands out there. They have an excellent price to performance ratio.
To sum up - I think the following "keywords", in addition to the ones already discussed, probably also best describes Klipsch and worth exploring in your design goals for this project:
Dynamic
Clarity
Value
Also, one of the marketing slogans Klipsch has used recently was "A Legend In Sound". Maybe something there you could take a cue from.
Also to add - how would this all compare to an experience I'd like to get out of a vehicle. I guess if I wanted to get that same "Klipsch experience" out of a car, I'd want something that would be fun and easy to drive, That it could take corners with precision, that let me feel the road with clarity, like I am actually part of the machine (much like how the Klipsch often make me feel like I am actually experiencing and being a part of the performance instead of just merely listening to a record through some speakers) . Also, the vehicle must be able to perform with all kinds of different road condtions, much like how the Klipsch does so well with all different types of music. I've heard metal, jazz, and classical on my own system and thought how awesome they all sounded (well, except maybe rap, but then again, I think rap sucks regardless what its played on - you could only polish a turd so much, but it is still a turd). But at the same time, it must be effiecent, but with plenty of power. I could stomp the accelerator and it'll get me from 0 to Jail inside of 5 seconds (crank up these Klipsch to loud, and the cops will definitly be at my door, but they maintain that loudness with incredible clarity and detail - no distortion - this is were the "Power" comes in), but the thing is not sucking up gas like a marathon runner sucking up water on a hot day, much like you don't need a kilowatt amplifer to get serious concert-level sound out of the Klipsch. At the same time, another aspect of Klipsch is that they offer an awesome price to performance ratio, which the likes of Bose cannot even begin to touch! I've paid around $1,800 for my RF-7s, but I've heard speakers that cost three or more times as much, but still prefered the RF-7s. Basically getting Ferrari performance, but at Honda prices with the Klipsch.
Will be interesting to see what you eventually come up with. I'll have to keep watching this space to see.