Well, kinda difficult to answer...
I'm pretty familiar with Ska, all the way from it's Jamaican roots as the precursor to Reggae. through the English TuTone revolution of the 80's to its rebirth in the late 90's. I don't remember it as being as bass heavy as Dub or Dancehall so I don't think you need a speaker "specially designed" for heavy bass. A speaker with good firm bass and decent mids for the horns would be your best bet. There's lots of speakers in your price range that I think would handle your music. Cambridge Soundworks makes a good line of speakers as does Polk and others that have good mids.
Hope this helps...
Da Worfster :cool: