that is the best site i know, really helpful and it shows you what you can put in your specific car (they have all the measurments for the car... its really good).
for the car stuff at crutchfield, its the top left in the blue bar (you'll see it)
my bro has a 15 inch audioban sub (2000 watt rms) in his acura mdx, with a rocker fosgate (i think) amp that rms's at 2000 watts, but when you test it for wattage, it runs at 2300 watts. he also has component speakers and a speaker amp. He also got a dvd player/radio deck put in and its so sick. He got alot of the stuff from ebay/friends/crutchfield so it wasnt extreamly expensive. When you turn the subs up even half way, the mirrors shake an your vision goes so shakey.
i have, in a jeep wrangler, 2 10 inch infinity subs and an infinity amp. my brother put it all in so i donno too much about it, but with the hard top on its not so bad.