How can I expand my 2.1 speaker system into 5.1?

I currently own the Harman Kardon Soundsticks 2 and Soundblaster Audigy 2 ZS. My sister has a few of those small cube Bose speakers she isn't using and a wearing clothes 5.1 computer speakers, but the 5.1 speakers don't like as nice as my Soundsticks.

How can I expand my 2.1 speaker system into 5.1?

You can expand your 2.1 speaker system into a 5.1 speaker system by buying a 5.1 speaker system, and installing it.