Patrick, you didn't say what kind of music you listen to, or how loud. The story with the 3.7's (and other Maggies) is that they're an easy amp load for a real amplifier (e.g., one that can double down into 4 ohms rather than a cheap receiver), but inefficient. Often, you'll hear talk about limited dynamic range in Maggies when someone just hasn't used an amplifier that will drive them to their potential. They can happily suck up 1000 watts per channel. But here's the thing -- people tend to turn them up at the store, but not at home. So most people don't need an amp that size, something like 250 watts per channel will do for most listeners. But it's impossible to say for sure without knowing how loud you listen.
In general, I'd say go with the 3.7's if you're concerned with stunningly realistic reproduction of acoustical music played at up to plausible levels. If you want to play rock at gut-thumping levels and have more of an instruments-in-your-listening-room effect, dynamics (or larger planars) can be a better choice. The Maggies by way of contrast are magic carpet speakers that if properly set up will transport you into a larger acoustical space.
I'm a line source dipole fan myself -- they have a realism on acoustical music that boxes lack. But this is my personal bias and I agree that you should listen to both, because preferences vary. Unfortunately, Maggies require careful setup and the box-oriented acoustics at most dealers don't suit them, so unless you have a friend with a pair it will be hard to hear them at their best. That's a consideration at home too, you have to be able to pull them out 5' from the front wall if they're to perform at their best, and they need a fairly plain wall behind them to image properly. Forex, I can't use them on the wall that has a fireplace mantle, the image isn't as good. If you can give them that and take some time with positioning, they're less sensitive to room acoustics than boxes.
