SP1 adds 192KHz support, but 96KHz should work without it... and if you have SP1 anyway..
Do you mean it's greyed out completely, or just that it keeps changing back to 44.1? It seems to function more like an indicator than a selector.. it switches automatically to whatever sampling rate you are playing.
Anyhow, I think the quality for playback would be the same unless you actually have some 96KHz music on your computer.