I want to upgrade from my hk-system!

ok, here goes....I know barely anything yet about subs, except from what i've seen in my friends cars, but i havent really figured out anything about good amps, subs, and speakers. SO, what is a good combo for the back of my 2001 325i sedan? I want to remove the rear deck speakers, i've heard alittle that the jl stealth boxes are good. What amp is the best? MONEY IS NOT AN ISSUE! I want good quality speakers, subs, and amp for my car, nothing less. So what amp would be good? Should i get another sub in addition to the two 8's in the stealths? IF i get the stealths. Someone tell me on a good setup that can be totally in the trunk, i really dont want to upgrade the front door, and back door speakers yet. Who makes the best quality subs and amps?