Best sound system for ipod docking �200 or under?

i want a stereo system to play mainly my ipod. i dont know what to go for though, i listen to a lot of dubstep and heavy bass house music, so i want something with really good bass. As above my price limit is �200. links to amazon or argos or somin would be much appreciated. and why do people say about dubstep and subwoofers, whats that about? please help me out