In all my dealings with churches and audio equipment, one rule stands above them all. It MUST be idiot proof. People who don't know what they are doing will mess with it, albeit with good intentions, so it must be so simple that it can't be messed up. Having said that, for a crowd of 15-30 people, I'm wondering if an AVR paired with high efficiency speakers might be a better route than live sound gear.
If one were really worried about output, couldn't you theoretically use an AVR with pre-outs run to pro amps and pro/live sound speakers anyway?