well, heres my info on daewoo lanos install.
right, it can sound shit having speakers in the rear overpowering the fronts. this is something best covered in general on an audio site.
now, i have put 5.25 front components in my car, and they sound wicked. i also have 6x9s on my shelf,
6x9s only usually work well on a shelf, as they use the boot as an enclousure. and if you put them in the rear quaters, or anywhere else, they wont sound as good. also, if you put a sub in the boot it will be creating pressure in the boot, which will be acting against the 6x9s speaker...so you have to be careful what you do.
i have stripped my boot out, and installed a sub and a few amps, and i have found i can probably squease some 6x9s in the stock locations, with the fabrication of a mdf ring.
anyway, i will be posting a huge topic/how to guide when i finally finish my install, and you can all see.
EDIT, HERES SOME PICS OF MY SHELF, IT CURRENTLY ONLY HAS 1 PAIR OV 6X9S, BUT ITS BEEN COVERED IN BLACK CARPET, AND LOOKS WICKED, YOU WOULDNT KNOW IT WAS A STEALTH SHELF.