| Just to put my 2 pennies in.....
Alpine makes great decks. Most people buy them based on reputation, but there is a reason they have a good one. I have sold and owned Alpine for some time and highly recomend them. They are one of the few companies left that are highly specialized (they make car audio and car audio only). I now have a Nakamichi just because I have turned into a sound snob and think their headunits have a noticeably better sound than most (their illumination also matches the BMW amber almost perfectly which gives it a undestracting oem look). Keep in mind they are built for sound not for compatablilty, so if you are buying a radio for compatability (i.e. cdr, cdrw, MP3, etc.), don't even think about Nak.
As for speakers, I think you would be hard pressed to find a three driver component set up to replace your oem set up for any kind of reasonable price. I might recomend purchasing a two driver set up (tweet and 5.25" mid) and just forget about your other door speaker. This is much more cost effective and upon completion, you will notice better sound quality than the oem three way set up. As for brands, Infinity, PolkAudio, MBQuart (in that order) are decent choices. If you have money coming out the wazoo, look at Diamond Audio, Polk Momo, and Focal.
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