There are lots of great choices; it really depends on personal taste.If you had an old HBI and DGT, what would be your 3 PRS guitar solution to the covering the most tones with 3 guitars?
I'd get a Singlecut. The extra mass of the body, and stiffness of the neck due to the upper bout extending farther upward seems to matter and give the guitar an oomph that's characteristic of SC style guitars. Maybe a 594 SC.
Or for a different flavor, a Custom 24. As others have said, a Soapbar model is another different sounding choice, and PRS soapbar models are terrific examples of the genre.
I think your DGT covers most of the bases a Hiland, older CE or SAS would.