What subs should i choose?

i am looking to replace my two 12" MTX 12-04's. they are only rated 200w rms a piece (thats what is printed on the magnet), and cost $130 per sub... why is that?? and second, i want to know what subs i can get. they need 4 ohm DVC, and be about 1000w rms/ pair, because i just bought an amp that pushes 1000w rms at one ohm. thanks!