What 12" sub should I put in my car with it being hooked up correctly?

I have Rockford Fosgate Prime r500 mono block that can be wired for 2 or 4 ohms. I used to have a 2 ohms 12" Polk Dxi that just blew. Would it be hard to rewire since its already up for 2 ohms to get it wired for 4 ? HELP ME ! Imma noob