Since your in the music biz, your ears will quickly inform you that a jeep wrangler is possibly the worst platform for a sound system made. Between driving a box through the wind, and the cavernous body with no great place for speakers... it's always a compromise. That said, the best way to get a band to sound good in a metal barn is with decent components and a lot of volume. Rock on.
An alpine head unit with an alpine 4x55 amp (under the passenger seat) is a great place to start. I just ordered Polk Audio speakers for dash and sound bar. A powered 8" sub under the driver's seat rounds it out quite well.