I agree with chill. Invest in a small PA mixer and a pair of speakers. My band uses the following;

A Soundcraft GigRac 600 and a pair of these SoundTech ST15s;

I liked the sound of these so much I bought 6 of them! I use the other 4 speakers as floor monitors for our main PA rig.
Loud enough to hear the vocals at practice and can even be the main PA at very small gigs. I also use this rig for my church's Sunrise Service. I bring the preacher's wireless mic and hook it all up to one of these;

With THAT rig you can do a live PA ANYWHERE you want!
We can also use this rig as a seprate monitor rig in situations that require more than we normally use. It's a very versital little system. Sound great, and it's suprisingly affordable!
By the way, the little generator is graciously provided by the radio stations I work for during the church service. It's the most expensive part! About $1000.00! You can get the speakers and GigRac for less than that!