type R's everyone here likes them...it really depends on how much you really want to spend...check out the classifieds you can find yourself some real nice subs for cheap...
My last setup i used 2 infinity kappa perfect 12.1 and they sounded great but they lack output and durablility. A common problem with the perfects is the tinsel leads snap from the terminal. I am now running 2 trype r 12s and they are much louder than the perfects SQ is basically the same and they are much more durable. The type r's are a much better bargain.