want to replace entire mach 460 system need help

im thinking about replacing the entire sound system in my 2001 mustang gt but im pretty clueless about sound systems. I was thinking of just doing a new headunit all new speakers and an amp, and leave the sub for a later time or if i have the money i'll do it together, what size speakers and how many of them do i need. Im going to be buying everything online and my friend is gonna install it for me. When i went to some local sound shops they said i should do 2 6 by 8s in the back and 2 in the front, i think he said to get 3 way speakers and bypass the factory door speakers but just leave them there for looks. What are some good speakers, im not lookin to spend a fortune just much better sound, i was looking at alpine stuff like type s speakers.

o yea i know this isnt alot at all but im trying to keep it under $700, keep in mind it without the sub i'll do that next year

here is what i was gonna get the alpine CDA-9853 headunit, alpine type-s speaker 2 sets, 2 for front 2 for back, an alpine 4 channel amp. Should i get 2 way or 3 way speakers or just do 2 way speakers all around?

should i go with components of front and 2 way speakers in the back. I heard some infinity kappa speakers and they sounded really good