I would say put your mains up front on the left and right side. Mic the the guitars and get a DI box for the bass, but essentially you want to get everything going through the PA so you can get an even mix and have independent stage and main volume controls. Also, with the everything going through the PA, you can point your guitar amps wherever you like (I point mine at my face) and that really helps out if you don't have enough stage monitors.