I currently have my pioneer receiver (vsx-519v) ran threw my computer. on board sound 5.1 asus p6t deulxe. my problem is when i play mp3s it will only play out of my front left and front right speakers and not threw my sub. i know mp3s are "sterio" sound and not full dolby 5.1 but shouldnt my sub be playing? my receiver is ran threw the multi-in function. sounds great on bluray movies but mp3s is a killer. any1 know what this could be?