Parson ...

Yes, a lot of bluegrass flatpickers have Martin dreadnoughts.

A lot of bluegrass flatpickers also have Santa Cruz, Gallagher, Collings, Bourgious (sp), Walkers, and there are a few more.

Wood is important, too. Rosewood has wonderful overtones and is a favorite wood for flatpickers. Mahogany has a more balanced tone and may be better if you are a singer, as well.

My advice would be to take a sufficient amount of time to play as many guitars, from as many makers, as you can, before you make a decision. In the end, you may find that a Martin is what you want, but you may also find that another make is what you want.

I will pass along the advice recently given to me by a friend:

"At least if you hate the sound, you won't ever have to wonder."