I think it all depends on what you want, what's best for you. I have 2 12" Infinity's that are perfect for me: sound quality, price, appearance, etc...
That a look at these sites, you might find something you like, or a review of the subs your thinking of getting:
ecoustics
Car Audio Review
Sound Domain
epinions
bah...too many sites to list...just try this:
Google search