As long as ya'll don't try to play with your amps wide open, and your drummer doesn't try to kill his drums, that should work for vocals only, but I wouldn't run anthything but the vocals with the PA. I've used some Yorkville 1x15" PA cabs, and I wasn't very impressed at all. Again... 15"'s don't work well for just vocals. It's also much better to have more watts than you need. Underpowering your speakers and making the amp clip can damage your speakers. You don't want to get something that you'll outgrow after a couple practices.