I bought a Creative SB Live24 USB sound device over the weekend and connected to my PC this morning.
I am quite impressed with the SQ on this cheap device. Using my Senn 555's it sounds quite good, but I suspect it does not have the real power to drive them so I connected my Senn 415's and it sounds very good.
Based on the price of R450 this device is an excellent value for money upgrade to builtin soundcards.