I just put a 'hard-wired" FM modulator in my 2004 SE S/C - It sounds better than the wireless FM modulators/transmitters but still sounds much worse than a true Aux-input.
I'll probably put in a new Head-unit. I want to be sure that I won't have to remove/replace the factory amp and speakers, and that I can make the steering-wheel control work with one of the available adapters.