Some random and quick thoughts:
In the East, I think you would include Tufts, JHU and Trinity, Ct.
Personally, I don't believe Southwestern is a high quality program. It is coming back from about a decade of decline and has a coach who turned around Hendrix. I would equate Southwestern with Oxy in baseball at this point.
In the South, personally, I would add Millsaps in Jackson, Miss. over Southwestern (by a pretty good margin for baseball and very close academically.)
The midwest has a number which probably should be included-Schools like DePauw.
Hopefully BishopLeftiesDad will post because he can add a wealth of information about the middle of the country.