GenVibe - Community for Pontiac Vibe Enthusiasts

I'm thinking about replacing the radio with an MP3 player. But I'm told I'll need to get a 1.5 din or a double din, or some sort of din thing going. Any idea what the heck this means?Where does one get the mounting brackets for whatever size?

Refer to: http://forums.genvibe.com/zerothread?id=947