normally u want 2 to 4 times the power for subs as a mid-n-tweeter combo, people get hung up on specs, 1000w. is huge and 2000 is incredible for car audio.
many companies over inflate ratings to sell their amps and even so called experts get fooled in the ratings game.
a mid to high end amp with specs of 40 to 100w. per channel should be good for mids-n-tweets, half that for just tweets.
subs should be 250w. to 500w. per channel.
in the old days high end amps designed for competition were under rated to get into watt classes, under 100 101 to 200 and so on, but there are also companies that cost 1/4 for an amp yet cost 4 times more.
just buy mid to high end products and use the specs as a rough guide, get a 2 or 4 chan amp for mids and tweets and at least double the power for the subs with a seperate amp.