I have a pair of Coincident Troubass. They serve as the stands for my Digital Masters, kind of like the Wilson Puppies sitting under the WATTs. The Troubass perfectly match both the Troubador and Digital Master, and make the appropriate stand for either Coincident satellite.
Personally, I like them a great deal, even though they're not nearly as efficient as Israel claims. I can say they're down a few dB from the satellites. With my Digital Masters, they're not exactly necessary, but having that last octave on the bottom provides the music with its foundation, which adds a nice bit to the end result. I don't always have them hooked up, and when I don't, I can't say I couldn't live with the sound as is, it's good enough. They definitely fall into the camp of "a good sub is only noticed in its absence" type of subwoofer, as opposed to the wowie zowie, look at me type.
They mate well enough with moderate power tubes, though the 10" Peerless drivers in the large vented cabinets provide close to blow you back kind of bass with the right solid state amplification. I definitely feel the matching satellites are best served with transformer coupled tube amplifiers.
I don't mean to seem like the negative type, but you're going to be extraordinarily hard pressed to find a pair for sale (I wouldn't sell mine for 10X what I paid for them), let alone in whatever finish matches your Troubadors. I don't ever remember a pair of Troubass coming up for sale here on Audiogon. A person or two has told me they approached Israel about having a pair made, and they were refused, though I have no first hand experience with that. Should be an easy buck for him to make, unlike the Troubador or Digital Master, each of which have no parallel sides, as the cabinets are very simple and straightforward.
Good luck!