basic system into 99 4runner

Hi, I just bought a 99 4runner and the cd player is shot so I want to build a budget system thats fairly simple but still sounds good. My plan right now (with minor knowledge) is to find a used Alpine deck because they have always served me well. In the doors, I'll go with a decent 6.5 speaker(component set?) and a 10" sub in the back. Open to opinions (I'm a newb so keep it real simple)....

1. Should I run the front speakers off the deck?

2. Is one 10" sub good enough? I listen to mainly metalish music. I plan on building my own box.

3. Do I need speakers in the rear doors?

There is no way to get 50 watts of power output from a 12volt supply (without a switching power supply).  Newer decks for the most part, all put out the same amount of power.  Unless of course you spend 50 bucks on it and it was hanging on a peghook.  Any 4 channel amp will be capable of running the doors and a sub.  Buy what you can afford now and then later you can buy a mono amp to run the sub and use the 4 channel on the front and rear.   As far as amp reccomendations go the new Alpine stuff is really good.