Nick,

Coming from GBS as you are, I'd start with Pint & Dale (available on iTunes, no less). They have a similar mix rock & roll and traditional sensibility with a number of their tunes, in addition to being great musicians and nice people. (Incidentally, I think they serve play a really valuable role for sea music in reimagining the old songs to keep them from calcifying into standard modes of performance, but they also, as they say, rock.)

As a transplant from Seattle to DC, I was going to chime in on NW musicians if Matt hadn't, but I'll just reinforce the recommendations for Hank Cramer and The Cutters (Philip & Teresa Morgan and sundry children and friends). Great vocalists, the lot of them.

JS