I have a '93 Ford Taurus which currently has the stock AM/FM radio for sound. I am using an FM transmitter to play music from my iPod but the quality leaves something to be desired. Also, I have very little money and was hoping to get something working for less than $50. Eventually, I'd like to put in some old hardware I have lying around and make a car PC out of it too. So I see a few options:

1. I have taken out the OEM radio and looked at the circuit. I couldn't see any obvious spots to try to add an input jack nor could I find a guide online. Is it worth poking around in there some more to try find a place to add an input?

2. Buy a headunit. This would be the simplest choice but the most expensive and I have not been able to find one for less than about $100 with an aux input, even on ebay. Is it possible to find working headunits around, perhaps in junk yards etc.?

3. After doing some thinking, I realized that a car amp might be just what I need. From what I can tell, it takes a signal in from an RCA cable (probably not the right level?) and drives speakers from it. Car amps are cheaper from what I've found and would make a good upgrade for my sound system.

Thanks for any help!