Single 12. Sealed box. Around 400-500 watts peak mono block amp.

This is considering you buy a good sub...
some of my favorites are MTX, Hertz, Diamond Audio, and RE.

The box type depends on what music you listen to. If you like big bass and hip-hop, get a ported box. If you like rock/metal and a more theater-like sound, get a sealed box. Stay away from bandpass boxes, no matter how "cool" people think they look.