fourthmeal, I would prefer to keep the headunit when I get the chance to upgrade my sound system. How does that work? I'm audio-technologically inept.
Its complicated in that the stock HU adds distortion that affects the rest of your system build. I have covered this a few times on the forums, do a search for my posts and soak that stuff in, then we can cover more in depth specific to your issue.
I'm all for keeping the stock deck if you MUST, but remember it is severely limiting the sound quality potential. I wish you guys could hear my truck...the thing has a strong presence and a really wide and deep soundstage that brings you right to the music. Replacing the stock deck, adding processing power for time alignment, using quality front separates (woofer / tweeter), a decent sub, heavily deadening / sealing the doors and trunk area (against rattles, resonance, all that), and having a decent amount of power on tap is what it took. But man the results speak for themselves. It just depends on how good you want your music to be in a car. Not LOUD, but how real, how natural and effortless do you want it? Loud is easy, getting good is tough but worth it.
You can also get all the goodies you want, like iPod hookup, bluetooth connection, etc. etc.