I bought our PA and we went down the route of mic'ing up everything, drums, bass, guitars as well as vocals. We used to do this in every pub we played in. Then one time we got a gig quite a drive away, so we decided to not take the bass bins and just put vocals through the PA. What a difference. We were balanced and had a decent volume without being ear splittingly loud. Everything was clear and we could hear each other. I realised that we were over killing our sound in small gigs. A vocal PA is good enough for most venues. If you get bigger gigs then putting everything through the PA is justified. People like to hear a band but still be able to chat.