Re: Shaker 500, worth $440?
I like the Shaker. The dual subs are nice, and it sounds good. stereo has lots of nice little features in it too when you start looking through the options. But, I'm a guy that has only had lower end Pioneer $150 head units in a noisy Jeep, so...YMMV. I also love the MP3 compatibility. It is awesome to have nearly my entire music collection on hand in the Stang!
It sounds like you would rather have Stang #2, so I would get that, and do an aftermarket stereo. Or heck, see if the dealer can add a Shaker to #2.
As far as the speaker count. It's 8. i had to crawl all over to find them all. You have 2x Subs, and 2 6x8 or 9s above the subs. 2x 6x9s in rear deck, and 2 somethings down low in front of the back seats, near where the front seatbelts come out. 'Verts could be different.