New Subwoofer

I can buy a Polk Micropro 1000 for 330 at Newegg and would use it with my computer, I have a PSW505 in my HT. If I can get a better sub than the 505 in my price range I will buy that instead and move the 505 to my computer or use both in my HT.

Like to stay around 330.
polkaudio SRS3.1TL
polkaudio CS350LS
polkaudio LS f/x