I bought a Martin HPL guitar (DXK2) as a "take it anywhere" guitar. In order to get the "decent" sound that would be the most satisfying I went for the dreadnought size. That turned out to be a good move. Now, it isn't a D-28 Marquis, but it is surprisingly satisfactory for the purpose for which I bought it.... places with high humidity and temperature. One of its surprising assets is the sustain.... it rings on for years. Not as "mature" sounding as a D-28 and variants of course, but pretty decent, and with plenty of bass response too.
and here in the heat and humidity on the beach and jungle of Malaysia a few weeks ago.
Rod