And if you're into really high quality, you would be going the full amps 'n speakers route, you wouldn't be considering chaining it into your factory stereo in the first place.

I'm assuming that since the person posting the first message in this thread took it to an installer shop and asked them to make it work with their existing stereo, that they don't care too much about super-high quality and they just want it to work. In that case, the FM modulator fits the bill quite nicely and will give them decent quality with a minimum of hassle.

Assuming both stereos fit in the dash, that is.