First of all I'd like to thank everyone for answering my various other questions, and I'd also like to post one or two more. Currently, everything in my band practice sounds fine except the vocals, which are too quiet, muffled, and screech every few minutes (the terrible feedback screech). I can only assume it is because of the PA system, because I am using a Shure sm57 mic, which is supposedly the industry standard for vocals (on a small budget, that is).
My question is, what microphone amp (or PA system) has good quality and can compete with drums and 15 watt guitar amps? Obviously I don't want to break the bank, so I'm just looking for the lowest passable amp that is loud and has acceptable quality (doesn't make your voice sound "bad," like a football game announcer or something.)
Thanks again to everyone for all the help; I'm already loving this forum after a few days.
My question is, what microphone amp (or PA system) has good quality and can compete with drums and 15 watt guitar amps? Obviously I don't want to break the bank, so I'm just looking for the lowest passable amp that is loud and has acceptable quality (doesn't make your voice sound "bad," like a football game announcer or something.)
Thanks again to everyone for all the help; I'm already loving this forum after a few days.

It was my mistake to go with some no name brand rather than a good one.