A small battery powered amp makes a world of difference. I have a little Vox amp and play acoustic guitar and use a headset vocal mic. It just gives you a little more volume so that you can be heard over surrounding noises. Without the amp, you have to pound on the guitar to even be heard. And forget about playing any kind of decent finger picking or lead work. I also play harmonica, but that seems to cut through more than everything else. The vocal mic also picks up the harmonica well enough.