I am going to disagree with the JL sub. Over priced and not the best for the kind of music he listens to. I am going to recommend a alpine type r 12 inch sub for your setup or a Rockford Fosgate Punch stage 3. For amps I do agree with your phoenix gold amp or you can go with a kicker amp to save money. When you order your sub make sure to get the DVC 4 ohms which means there is 2 voice coils that are 4 ohms. This way you can hook it up to most amps.
www.woofersetc.com
or
www.amazon.com
are good places to get your sub and amp. Also do not forget your power wire and rca cables as well. I recommend kicker hyperflex 4 gauge for power wire and rcas stinger is pretty good.