I have a pyramid 1400 crystal series amp (yea, yea, i know its not exactly the best) and currently have 2 old 12" blau punkt subs. I am looking to buy some new 12's and need some input.

If i bridge my 4 channel amp, it says i can get 500x2 watts rms at 4 ohm. So I am lookin for some 250-500 watt rms subs i can run off my amp. I have a sealed box, and amp lookin for and sq, sp/sq type sub. Any recommendations are greatly appreciated, i have pretty much no clue what to get. Any sites to get the subs would also be greatly appreciated

-although i have heard "shiva" 12's are good, but run at 8 ohm.