It sucks that stupid car audio manufactures make all the modern 3.5 2 ways with protruding tweeters for some reason...like the woofer is actually going to have bass extension or something. I agree that CSII setup with a nice component set is probably ideal. The qlogic kicks are great for sound, but what happens to your ebrake? The rear speakers are terrible for SQ since the glass is right there. You def want a 2 way speaker at the most. 3 and 4 way speakers never sound good anyway. You can stick with 4x10's if you're running a separate sub. I never understood people putting ginormous sound systems in performance cars. Stereo equipment is heavy! 4 subs, 10 speakers, a box, amps...it's just silly if you're trying to go fast. Let's not forget the cars are "collector's items" so before you destroy a perfectly good set of original plastic door panels, or dash panels, dash board think to yourself "am I keeping this car forever?". I run all "oldschool" equipment in my cars since all the new stuff is crap. New stuff by PPI, Soundstream, MB Quart and Pioneer is garbage. There is no warmth to the equipment. It's all just Peak Power nonsense and specs that account for sound as plastic as Kim Kardashian's nose. You can't go wrong with an amplified Bazooka bass tube for quick, removable bass. The 8-inch 250 watt model will fit right under the rear shelf without issue and provide great bass unless you're trying to pretend you're in night at the roxbury...which in that case, shouldn't you be driving something more baller than a buick? I've been in the car audio business for 20 years and I can't tell you how many people with classic cars that I refused to hack their car. When they give me free reign to make their cars look OEM, but still sound great with quality equipment, they always thank me. "You want me to cut the dash of your '57 Chevy Belair with the factory AM, just so you can have a motorized TV screen? Um, no." Does that sound pretentious? Yes. Have I lost business that way? Yes. I still get a good laugh about all the TR dash panels my dad ruined in the 80's when he installed the Mirage/Code-Alarm keypad alarm systems. But then again, how many cars were saved by him in the process? And who thought they would be collector cars?
p.s. Believe it or not, the 3.5 inch speakers that come in the Chryslers with Boston Acoustics sound system aren't bad. They're actually run as mid/tweeters in the systems even though they're not "tweeters". Then again, Bose home audio systems never had an actual tweeter either and they were always highly regarded. I have one of the speakers handy I think the part number is P05059068AB if anybody would like to look one up. I'd imagine you'd want to run a bass blocker of at least 200hz considering the factory amp has a built in crossover.