Meet the Rubik Subwoofer (Elac MicroSub 2010 BT). It's bluetooth enabled, so you don't have to worry about messy wires being tangled, or untangled, but should you need to, you can connect using an RC jack.
Best thing about this 'Rubik' is there's no vibration, so it doesn't matter what kindof music you blast out of this cube, it ain't gonna affect the surrounding objects.
Price? Unavailable. But, one thing I know. It's only 4.7kg.

http://www.shinyshiny.tv/2008/09/rubiks_cubesubw.html