Also rears are 6x8
I recently installed a cheap pioneer head unit (like 80 bucks at walmart), and some kicker 6 1/2" speakers (60 bucks a pair). Sounds great for the price. Re wire isn't too bad, and junk the stock system completely.
To be honest you could get away with just two door speakers, the sound is more than enough for a small Fox. But if you must, do the doors and the rears. Dont worry about the dash.
2000 Mustang GT-Former giggle gas addict
1990 Mustang GT w/ Vortech V3
***resident gun idiot***