[madness410]

im looking to drop a few bucks (well, actually whatever it takes) into some speakers all around in my 87 camaro. right now i have two rear sony speakers, which are loud and get the job done but im a big music buff and would like to hear some type of quality. so i have a few questions..

what are the basic things to look for when on the market for speakers?
does anybody recommend a certain type?
does your headunit play a major part in deciding what speakers to get also