So i just picked up my first FTO on the weekend , and I must say , im a proud owner now

The things so stock its not funny ... its a 95 GPX , stock wheels , stock stereo , stock everything ... done 66k Klms .. But thats how i wanted it , my last car cost me a fortune in maintenance ...
Anyway to my point , the stereo is blown to pieces ... speakers are crunching , and its just dead in general...
Im going to replace the entire system , and iv begun buying gear ... So far iv got 2 x 350w Alpine VPower amps , which ill use for the 6x9's in the back and the door speakers , along with a sub in the boot ...
My question is though , can any of you guys give me some advice on a good setup ? ..
What size are the door speakers ? . Which door speakers should I buy ? .. and 6x9's ? .. I was looking at some Alpine 5cm Tweeters to replace the door tweeters near the window , is this just simply a cut&paste job ? .. Im guessing ill have to loose the standard stacker if I buy a new stereo right ? will there be a standard size for stackers that I can just replace it with another one with minimal effort ?
Just looking for some pointers from you FTO veterans before I start ripping stuff out ... I want to do this right ..
Cheers !
- Cheyne