Ross,
I'm curious as to which Xonar you bought. I have a X-Fi Titanium Fatality card, and while it is an ok card for games it is lacking in multimedia using Windows 7 64bit. I only play games occasionally these days and use the system more as a multimedia pc including bluray and HDTV viewing. There are currently 10 listed at NewEgg and I am considering pulling the X-Fi and getting a Xonar myself. Do you have a link to the particular card you acquired? Is it PCI or PCI-e?