Both Maggies and Martins are fine speakers.
One of the lesser-known, perhaps more esoteric, kids on the block is Sound Lab. While best known for their world-class full-range electrostatics, Sound Lab makes a hybrid called the "Dynastat" for a bit under four grand. While conceptually similar to the Martins, there are a few differences - for one thing, the Dynastat's electrostatic element radiates over a 75 degree arc instead of a 30 degree arc and so gives you a wider sweet spot and a better energized reverberant field, at the expense of greater sidewall interaction. The Dynastats go pretty deep (27 Hz) as well, and the woofer-to-panel integration is in my opinion very good (because the panel's radiation pattern is more similar to the woofer's). The Dynastat also has an abundance of controls, useful for optimizing for different rooms, listening distances, systems, and preferences.
If by any chance you are in the price range of the Maggie 20.1's or Martin Prodigy's, then you might want to consider one of Sound Lab's full range electrostats.
You can check them all out at www.soundlab-speakers.com, or drop me a line with any questions you may have.
The InnerSound speakers mentioned by Angela100 are very dynamic and have superb imaging, but a very narrow sweet spot. I prefer the wider radiation pattern of the Dynastats, but it's very much a matter of personal taste. The InnerSounds are also equipped with a variety of useful controls.
All four of these lines - Maggies, Martins, InnerSounds, and Sound Labs - are in my opinon significantly more musical than virtually all box speakers in the same price range. They have different virtues and so appeal to different listeners, but if you love the boxless sound of planars, then from among their ranks you can probably find the speaker that's right for you.
