I always liked classical, so I probably would've found much of the classical I've heard in drum corps at some point anyway - though I was certainly introduced to a bunch through drum corps. There are some deep cuts that I likely never would have stumbled upon because they're generally not played by orchestras: Shosty's Ballet Suite #4 or Fire of Eternal Glory, Copland's Organ Symphony, Hanson's symphonies, Barber's Medea, to name a few.
I'd say where my tastes expanded specifically due to drum corps would be in jazz. Stan Kenton (though he's famous), Don Ellis (would not have understood the title tune to Whiplash), Pat Metheny (he'd just be a guy that thinks Kenny G sucks), Chick Corea, and the jazzophonic stuff Xmen was doing in the early-to-mid-90s.