In the front and rear doors, you can fit 6-1/2" Speakers, the head unit can be any single din unit (that means just about all CD players made) and for the subs and amps, that is totally up to you...most anything will fit so long as you can afford the install. If you are looking for a kickin system, I would not reccommend buying anything real low end and if you can afford it, the following brands are real good:
Head units: Alpine and Eclipse
6-1/2" Speakers: MB Quart, Focal, JL Audio, and Polk (The Polks are a budget alternative)
Subwoofers: Kicker, JL Audio, MTX, Polk MOMO, and Orion (The Orion is the loudest of of these but not much sound quality)
Amplifiers: A/D/S/, Xtant, Eclipse, Kicker, JL Audio, Phoenix Gold, and MTX
Any combination of this stuff will yield a pretty good sounding system. But make sure to have it professionsally installed (Not at Best Buy or Circuit City).
Check out this site for good deals:
http://www.sounddomain.com
Good Luck!
SZ 314
PS - Two subs can be a lot...1 12" Kicker L7 or 1 JL 10 W7 will be freakin loud.