WHY WOULD YOU BUY a TWO WAY SPEAKER AND BUY EXTRA TWEETERS!?
DEATHZONE: Damn, very nice setup, cant wait to see it/see pics! :D
BLADE: Mate I hear you. I understand where your coming from, basically as stated in my post, To each their own.
ORROCK: Mate i know where you are coming from, but sometimes it makes sense to do the line-out conversion and run amps of a head unit. I was tempted for quite a while. Stock in the ZR, they give u a double din AM/FM/TAPE/CD - which includes the 6 disc indash player. DOubt you will ever find an aftermarket unit with the same specs/functions at a reasonable price. And when it comes with the car for free (well not really u paid for the car) why throw it away. like i said mate, Everyone has their own ideas and preferances. I still upgraded the head unit anyway, and am happy with the results so far.
E-GENE: That head unit (7550) is pretty good man, you should be happy with the functions/stuff it will offer you. Just be weary if your going to buy it off Ebay.
Basically you would get decent sound with 2way or 3way speakers. Again its personal preference, three way speakers offer better clarity for sound (treble/high end, vocals etc). 2way still sounds good and gives the mid-range sound or bass that people like, but at times the clarity/treble/vocals can sound "tinnny"/flat.
In an attempt to make some kind of sense, think of two way as "one-way bass + one-way treble" and think of three way as "one way bass + 2 ways for treble".
Though this maybe grossely inaccurate, it'll give you an idea of what each can offer, but is better explained by listening to them. Run the same song, through a set of both speakers at a sound/car audio shop and you'll hear it for yourself.
-Sharmz.
BTW I work for Strathfield car radios