[oneHeadlight]

i m in serious lack of sleep but hopefully i catch u correctly...

u are gonna mod your door such that it fits a 6.5" midbass right ?
i assume your tweets are either to be mounted on A pillar or dashboard ?
there is a pair of 4" u intend to use ?
u will still use those funny stuff under the seats...?
u still wanna have speakers in the rear ?

this is wat i think....

forget about the stuff under the seat.
if u are going 5.1, then maybe u can spend money on the rear, else its not really necessary. If u still wanna have the rear, go for co-axials will do.

100w/ch, i assume its 100wrms. For tweets and mid (4") , its fine.
But for your midbass, its way way lacking.

350w into your free-air subs wouldnt be good enough. Free-air subs are alot more difficult to control, and usually u would want ALOT of power into it/them. Go for as much power as u can afford, from a decent brand at least.