What kind of amplifier do I need for my car Radio?

depends on the radio, and depends on what you're looking for. Your best bet is to just upgrade all the car audio. Go with a new head-unit and speakers first. But make sure you get a good head unit. I suggest the Alpine Cda-9856. It costs about 200, but its well worth the money. Plus the headunit makes it easier to expand your system with amps and subs at a later time. Dont just add subs and amps to your factory system

I believe that if you plan on installing a whole car audio system (new header, new speakers, subs), you'll definitely need an amp. But, if you're just simply replacing your current cassette/CD player with a new header (your new car radio), then you will not need an amp. Hope that helps!

It sounds to me like you just want to get your FM stations in better, not replace your whole system. You can purchase an FM signal booster from most electronic shops, but, to be honest, they don't work all that great. They seem to amplify the noise as well. Best bet is to look for a decent head unit w/ a good tuner section. You don't need an entire system, just a better tuner for your existing system. Hope this helps.