DM is a solid spruce top; laminated back & sides. My understanding is that as long as the top is solid, you can expect it to "open up" over time, to some degree.

I would also vote for D'Addario PBs as being the most consistently good string around. If you find them to be too bright, though, try the D'Addario "True American" 85/15 bronze strings, which are also cheaper.

If you're looking to fingerpick a Martin dread, another string you ought to give a try to is GHS PB True Mediums (standard medium gauge on the two unwound strings and low E; standard light gauge on the other three wound strings).

Peter.