You can get a nice Kenwood, Pioneer, Clarion, or Alpine deck for $250 or less. Just find the one that has the features you're looking for that fits your budget. JVC and Blau are okay too but are a bit quirky for my personal tastes.
I don't recommend Sony. Unless you buy top shelf stuff, it's substandard (not saying that people haven't been completely satisfied with their entry-level stuff). BTW, AIWA is a Sony subsidiary.
You might also try used. For instance, I'll probably sell my KW eXcelon deck for $150 or so when someone finally makes a decent AND affordable in-dash CD/mp3 player.
