Ah...but WAXI is not in the Terre Haute market, at least as Arbitron defines it (and therefore the FCC as well). Parke County is in the TSA, but not the metro.
(For the record: Clay, Sullivan, Vermillion and Vigo counties in Indiana, Clark and Edgar in Illinois.)
Subtract WAXI and WSDX from the equation, and you've got a five-station cluster. The biggest concern there may well be the informal 40% revenue cap that the Justice Department imposes - it's not hard to imagine that WTHI-FM pulls a significant chunk of that all by itself.