Martin Retro Monel MM13's, drop the action a hair, and give them a week or two to break in - old-time tone for days...
FWIW I came
this close to buying that very guitar from Djangobooks (may the better/faster man win - use it well and often
); by way of information you're dealing with a mahogany-bodied instrument rather than the traditional maple, and as your guitar breaks in it's going to reflect its unique construction in a "warmer" tone ("rounder" bass, sweeter trebles) with more overtones and sustain - the definition of "modern" archtop tone, filtered here through a mahogany lens. Whether or not this is what you want in your instrument is up to you, but suffice it to say that the similarly-constructed, early-postwar Epiphone Devon has a cult following among discerning archtop aficionados for just that reason: the characteristics you cite are even more accentuated by the 17" body (and seven decades of aging) - if you're primarily a singer looking for a different flavor of accompaniment I can't think of a better archtop than an old Devon, and with some more break-in time yours should exhibit its family lineage in similar fashion...