Bob Landry,
There are quite a few portable amps on the market now. Your music store may know them as "Singer/Songwriter" amps. Most have two channels, one for a vocal mike and another for an instrument. Some give you a choice of XLR or RCA input on both channels, some only on one. Most have some sort of equalization and either a built-in reverb or at least an "effects" input/output.
I have a Centaur I have used for gigs. It does very well in a Starbucks-like situation. I suspect it can push quite a bit more and fill a larger room. Don't know if it could handle a bar.
I have been very happy with it. My roadie fiancee can easily carry it and I have been very pleased with the sound. There are many variations on the market.
Roger in Baltimore