Mp3 Car Audio without Stereo - DIY - ideas?

[BlueRaven]

Like many of you out there, I have recently come to own a hard disk based mp3 player (although i've had two before this, they were both small flash based ones and utterly useless for what im trying to do here). As it holds 20gig of music files and currently over 3,300 songs - I've taken to listening to it everywhere.

I no longer listen to CDs and at my computer I plug the speakers into it instead. It is my full-time music buddy.

I bought a tape adapter for my wife to use in her car as well, as its 10x better than FM ones (when you have the option of using a tape adapter).

The question came to mind, how can I add a aux port to an existing stereo to plug it directly into a stereo....but then I thought of an even greater idea.

As it IS a project car, which means I can pretty much do whatever I want with it, why don't I ditch the stereo completely?? I dont need it and wouldnt use it.
What if I just plug the mp3 player into a jack? I've got a radio and mp3 player - so I dont need a car stereo. Besides, when a potential theif sees there isnt a CD player, I decrease the cars stealability!!

So to do this... im aware I need..

- cabling
- some kind of small amp?
- plugs and things

So what Im asking here, is does anyone have any idea how I could do this?

Should I butcher the existing tape fm/am radio (non original) in there to do it?

Could I buy a mini amp from somewhere?

What if I wanted to control balance/fade?

Bare in mind, this project needs to be as cheap as humanly possible - so its a bit of a lark. A bit of fun.