My computer only runs Crysis at 30fps any but when I watch the youtube video it runs faster. [/green font]
Music is encoded in 2.0/2.1. Just because you have 5.1 speakers does not mean they will all be used.
If you want all the speakers to play when using 2.0 sources, you either have to set some form of "Speaker Fill" option (which copies the L/R outputs to the other outputs), or enable some form of audio upmixing.