In doing Silverlight Simon and friends and then trying to port the uber tile from Silverlight to WPF I found that for doing quick short sounds there was a limit in Silverlight and WPF to the preformance and bahavior you can expect. WPF's 'MediaElement' is just horride but even in Silverlight if I try to use the same media element to play 2 short 2 second clips with in 1 second you will get issues.