I just joined my friends' band as the vocalist. Right now, I'm using my mp3 player's microphone through my guitar amp but I've found that I get a ton of feedback. I don't imagine that lugging the band's PA system back and forth from house to house is a good idea, but if it comes to it then so be it. I'm looking to purchase some low to mid-ranged equipment. Could someone point me in the right direction?
For some reason, I thought this was a "my dick is sore" thread. :X

I can't help you, but how are you using your MP3 microphone through an amp?
I have those Red/White AUX-In ports on my amp. I put the red and white ends of the cable into the amp and the other end in the headphone jack on my IRiver H320. If I enter recording mode without actually recording, it sends the sound to the amp.