What kind of speakers and amp/receiver are they? Generally, better cable can increase sound quality, but you need some high quality components to be able to notice the difference. Also, a lot of cable that is marketed as being high quality is nothing more than overpriced crap. I don't know anything about QED SA XT cable.
A final consideration is the length of the run. The longer the run of cable, the more beneficial it is to use a high quality product. Noise produced by inferior cable is going to be amplified once the runs start getting longer.