In the market to upgrade my car audio system?

[Ryan M]

I have a 2004 ford taurus, stock everything. I would like to upgrade my entire sound system so that it plays louder, catching all the highs, mids and lows well, and sounds great. I don't want a rattling bass in my trunk, i dont want any touch screens or remotes or anything, I just want to keep it as simple as possible, speakers, head unit, maybe a small amp. I have no idea how much any of this is going to cost me for a decent set, but I really would like to upgrade. Could anyone point me in the right direction as to what products I should buy, or what's most important for loudness, clarity and good sound? If I could deck my car out with an entire bose system i would. My budget is about 500. So my whole story here can be summed up in one question: if you had my car, and 500 bucks, what would you do with it to upgrade the entire audio system. Thanks!