Originally Posted by Chromeshadow

All of the shaker 500s that I'm aware of have 6 speakers, 4 6x8s and 2 8" subs.
some also may have small tweeters. All of the speakers except for the door subs are driven directly from the head unit. The 8" door subs require more power than is available from the main head unit and use an external map.
I replaced the external amp that came with the factory shaker 500 with a Sony amp.

The shaker 1000 included a trunk subwoofer with it's own amp, Shelby offers a similar trunk mounted sub.
It's good that you have a lot of questions, I would encourage you to go to car shows and look for; and listen to a lot of car radios to try and get some real life experience with aftermarket radios. I don't trust a lot of audio shops, I'm sure there are great ones out there, but it's easy to make your system worse if you chose the wrong parts or wire them in poorly. If you do move ahead, you may want to start a new post and ask if anyone here has tried the speakers and amp you plan on using and how well or poorly it worked for them. A lot depends on the music you listen to and what your preferences are, and if you need the trunk space. Some people want to feel the bass and set off car alarms, some want to hear the music as realistic as possible. Neither is right or wrong INHO. I set up mine exactly the way I want it, it's nice to get complements on it, but even if others hated it I'd leave it just like it is.
Btw, awesome car!