I know many of you have replaced the radio. I plan to do so also - I want something with an MP3 player, clock. And something that looks good in the Insight. Also, something that is EASY to put in, no cutting, etc. required.
My choice is the only radio that is as much technologically advanced, ahead of it's time and rare as the Insight itself. The empeg!
It's been discontinued years ago, but there is an alive-and-well community supporting it. And you find players popping up on ebay. Info here
Check Crutchfield to get some ideas, use the "what fits my car" tool.
There are quite a few CD/MP3 head units available and they have pictures so you can get an idea of what you like the looks of. There are many under $250 bucks, and really there won't be much performance difference at that level.
And installation is about as easy as it gets. There are pages where folks have shown how to pull the dash apart, and it really is simple. Much simpler than most other cars I have worked on.
Crutchfield even includes the needed harness adapter.