I'm guessing from the description that you're replacing the Shaker 500: good call. Speakers first for the most bang for the buck... actually there's a lot more room in the door panels than you'd think. You can easily replace the upper components with 5 x 8's or 6 x 9's with minor, if any, mods. Although the subs are pretty wimpy as built, there is room for upgrades. I replaced mine with 6 1/2" mid-woofers with plenty of space for the magnets (I tore the grills off of the stock speakers and mounted the smaller aftermarket ones behind to the grills so that I could mount to the same spot and still use the factory covers for looks). To the left inside the panel was a nice pocket to place my crossovers, packed in bubble-wrap instead of mounting them. Rear deck speaker replacement is only slightly difficult because there's little room to work; the grills pop off easily enough, but the rear screws holding each speaker are a real pain in the neck! You'll need a snake or ratchet screwdriver to get them out, but then again, either 5 x 8's or 6 x 9's fit right in. Keep in mind that the stock speakers are very light and require very little power (which is all the stock amps produce) to play loud. You can't get that volume with decent quality aftermarket speakers without over-driving the stock amps, so look to replace them next. IMO Good luck!