Have a look at the Carvin Stagemate – its only available from the factory in california – they have a website – I have been using mine with the effects unit for about 10 years – it has 4 channel mixer with one input specifically for acoustic – I use 3 pickups for bass, midrange, and treble and blend them with the treble pickup going to the acoustic input – I spent a great deal of time fiddleing with it to get a good mix, and for the most part, people don’t realize that I am amped even with the reverb on the treble –
I never never point a speaker at an audience – always bounce the sound off the wall behind me or the ceiling – for outdoor weddings I use one or two extra extension speakers 15-20 feet apart not for volume, but for coverage –
be prepared to spend some time experimenting with pickup placement once you do pick an amp – a change in your volume setting will change the response characteristics