I'm looking to get a car mp3 player.. I know little about car audio, and can afford little more than a nice radio at the moment. My price range is $275 and below. I have seen, what appear to be, some good deals on ebay, such as the Pioneer7400MP for $230.

What should I look for in a good head unit? The pioneer one says '22 watts RMS/50 watts peak x 4 channels', vs. a $130 45wattx4 Jensen. The pioneer says it comes with a built-in amp? Is that just fluff, or what "The built-in MOSFET50 amp will fire up your speakers."

I got stock speakers, but would like to get the most out of them I can. What stats should I be looking at for a head unit..?

And lastly, how hard is it to install one yourself...