To the OP: I'm not sure what your price range is, but this acoustic bass isn't half bad:
Fender Kingman Dreadnought
I played one at a Guitar Center about a week ago and I liked it a lot. It didn't have the intonation/fret buzz/high action issues most acoustic basses in the cheap range do. It also had good volume, but that's relative. Unless you want to fork out the dough for a Martin, you'll be hard pressed to find an acoustic bass with high output. That's why most have some sort of shitty pick-up in them.
If that's out of your range, you could always grab a Dean:
Dean Acoustic Bass
I bought one of these a couple years ago to keep in the living room for farting around. This thing is cheap as shit though. It has an ok sound and output, but the intonation is so fucking bad you wont be able to jam with anyone anyway. UNless everyone in your band is tone-def