Regarding the subs...either the amp is not powerful enough or the box is too large for the speakers. This will usually cause distortion. If you want to still have some good bass, try using only one of the subs in a box built exactly for it, and try a sealed enclosure, this usually gives the best sound quality.
As for the components, make sure to get a good quality set, like Image Dynamics, Focals, MB Quarts, or even Infinity or Polk Audio. These are all great speakers and will produce more more than enough sound. Dont run the rear speakers. The components are enough, especially if you get the 6 1/2 component set, these produce better bass resopnse than the smaller ones. The amp wires to the crossover and the crossover is wired to the separate speakers of the set. Simple enough.