whats the little amp for? does it just act like an equaliser?

My plan for the little $12 AMP is to...
 
- Use the original radio like normal
- Run a headphone jack between my iPhone and the line-in on the amp
- Put a subtle/tasteful switch somewhere to toggle output to the speakers between the original radio and the iPhone/amp setup
 
I want to hide everything and keep the original look. It took me a long time to find an uncut radio bezel, so I'm definately not going to be molesting the car

I can see why you would be dubious about that amp neil. As long as you dont push it too hard it will be fine. I suspect that the sound quality will be zero, and that 500w is peak rating. At that level, not only will you pop speakers, but you will cook the amp in 5 minutes. 
 
Running a cheap pair of 6*9 speakers on the parcel shelf at normal volumes, listening to ABC radio, yeah it will be fine.
 
An indicator for better quality in an amp (although not definative) is its weight. More weight indicates better heatsinks and cooling capacity. It it weighs nothing, then there arnt many heat sinks.
 
Still it will make some noise. If you need encouragement neil, we can jack up a time to wirie it in if you like. Im always keen to do some work for others. It means i dont have to work on my projects!