The interface hooks up to any avialable USB port... 1.1 is fine. This in effect becomes the sound card.
From the USB interface to the speakers any RCA cable will work fine. You could actually take any of the RCA cables that you get with standard DVD Players, Game Consoles, etc. Just split it in half and run one to one speaker and the other to the next.
I actually purchased higher end cables from Amazon but any RCA cable will do. Shorter the distance the better.
TRS would be better but then you would also need a much more expensive interface.
Here is a picture of basic cables from Amazon.... not an affiliate link http://www.amazon.com/Premium-Stereo-Audio-support...
The cables are male on both ends as the speakers and interface are both female.
These are higher end cables... better shielding should in theory sound better.