I disagree that our cars have crap speaker locations. The dash speakers, while semi-pointless, can produce some nice front fill. But yes, you really dont get any mids from a 3.5" speaker! In my GN, Im running Rockford Fosgate 3.5" w/ bass blockers. Since I PERSONALLY like more rear fill, the 3.5s are just kinda there for fun, running off of my Fosgate RFX-9220G source unit.
Moving to the rear. Ditch those 4x10s, and get some 6x9s and adapters! Every G-body Ive ever owned Ive converted to 6x9s. Heres where you get some of your mid and most of your "volume". I personally run some older Rockford Fosgate 6x9s and have an old school Punch 100x2 running to them. They LOVE IT! They are 100 watt RMS 200 watt peak speakers, and they just love the Punch 100x2 Amplifier. I started out with a Punch 40ix on them, then moved up to a Punch 60x2, now obviously I have settled on the 100x2 amp. Each time I upgraded amps/power to the 6x9s, they got a little louder, and a little clearer. I guess you could say I perfectly matched what the speakers liked. They absolutely scream and I love it, I have my source unit faded a little more towards the rear, thats just how I like it.
Moving to the sub. Ive had many different configurations of subs in my G-bodies over the years. 2 12s in a prefab box on the trunk floor, 3 10s under the rear deck, etc. In my GN I figured I would want all of my equipment up and out of the way, so I designed an enclosure and amp racks under the rear deck. I designed a sealed enclosure (my preference) that was centered between the 6x9s facing rearwards for a 12" sub. The enclosure is 1.27 cuft, which isnt bad for most 12s. Ive had a few different 12s and many different amps in the car. 1st was a JL Audio 12w6 on my Punch 200ix. Sounded okay, but wasnt what I liked. Upgraded to a Rockford Fosgate Punch HX2 12", and hated it. I read later than they work better in vented enclosures, so I sold it. I have settled on something finally. After 2 years of playing around, I think I have the combo I LIKE! Yes, I LIKE, I dont care if you like it, because somebody else said above, its what your ears like. I am running a Rockford Fosgate Power T1 12" sub, in the same sealed enclosure, with the legendary Rockford Fosgate Punch 500m amplifier. The sub is 600 watts RMS, 1200 peak. It sounds awesome. Nice tight punchy bass, but can hit fairly low too. All my gains are set up with a multi-meter, based on head unit pre-out voltages, and of course, how much power the amp is suppost to produce at full unclipped volume. It pounds with the best of them for a single sub system, but I feel it is pretty well balance for what I like. Eventually Id like to add some CSII panels and do some components for more mid bass, but what I have now makes me very happy.
For more info on this install, you guys feel free to stop by my sounddomain site. I need to update it, but you get the idea........ Hope this helps!
www.sounddomain.com/id/8uwith6