Ryan --
I'm certainly no expert, but I can tell you what has worked well for me, assuming you want to build a sound-quality system, as opposed to a "boomer" to impress the hell out of the chicks. ;-) (Nothing wrong with a boomer system, just not my cup of tea, that's all.)
I have had original Ford speakers; Blaupunkts; and Crystals up forward in my dash (round 4" or thereabouts) and finally went to the MB Quart RKB-100 4" co-axials. The difference between those MB Quarts and anything else I had tried is beyond description. They are not cheap (around $250 for the pair, I think) but they are absolutely the key element of my car audio system. I also have some other MB Quart speakers in the six inch range in doors and for center channel in dash.
Amplifiers I can't really advise you on. I am running a pair of PPI amps (a 100 watt amp for the small speakers, and a separate 50 watt amp for my sub) and they have been entirely satisfactory. I have had no experience with other amps. My impression is they're good, but not extraordinary quality. They sell for around $250 each, I think.
For your subwoofers, avoid the "bigger must be better" syndrome. Don't ruin the utility of your car by filling up the whole trunk with big boxes of subwoofers. My system has a single 10" speaker (running full spectrum, not crossed over like it is supposed to be, but that is another story...) and I don't think it is coincidence that at the IASCA state finals a few weeks ago the three cars (mine among them!) that were unquestionably the best in sound quality had nothing larger than 10", with a total of four ten-inch speakers among all three cars.
In my limited experience, the factors that contribute most to high quality sound are not the brand names and power of the equipment, but appropriate speaker size, speaker location, and the acoustic properties of the vehicle itself. (That last one is where bigger really is better -- the more air volume inside the passenger compartment you have to work with, the better you can do. It is really hard to get good sound in a pickup truck, for example. Vans and station wagons (yeah! wagons ;-) seem to work best.)
Good luck on your install and keep us waiting-queue-challenged empeg-wannabes posted.
tanstaafl.
"There Ain't No Such Thing As A Free Lunch"
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"There Ain't No Such Thing As A Free Lunch"