Has anyone had any success with fitting an amp and new speakers with the stock head unit. I know that an after market head unit is the best way to go for sound quality and to keep things cheap, but I without a doubt am going to keep the stock head unit. So basically what I'm trying to do is get a small amp and hook it up to the stock head unit and then buy some decent speakers that can handle the amp. Anyone gone this route before?
It's been awhile since I've been in the stereo installation business, but your biggest issue is going to be a way to get the signal from the factory HU to the Amplifier. You could use a high to low level converter, but they're not that effective. It really just taps into one of your signal wires and then gives you RCA plugs on the other end. Also, the signal coming out from the factory unit is pretty much garbage. and like they say - Garbage In, Garbage Out.
Another option is a setup like the Alpine F.I.T. system
Alpine Electronics of America, Inc.
It takes the existing signal from your factory unit, cleans it up, and then gives you a stable 'base' signal to send to your amplifier. It also provides a connection to use for your amplifier. It might be the perfect solution to your problem.
The drawback with this (or any other sound processing system) is you're going to spend some time (and money) getting it tuned properly. The IMPRINT technology that Alpine offers is pretty good, it'll get you close, and with a digital processor like this, it's nearly a necessity. It usually runs $40 or so if I remember correctly, and takes about 1/2 hour from start to finsh.
By all means, Alpine's not the only option available for you, but it's the one I have the most experience with. I think JL Audio also has a similar system available.
Hope this helps.