Just a note on Windows 7 build 7225. The most recent Xonar drivers for my DX seem to be broken in this release, while they worked fine on earlier builds. After installing the drivers and rebooting, Explorer windows would hang and require restarting the service. Removing the Xonar drivers cleared it up.
I'm hoping it's just a quirk with that particular Windows 7 build since we'll most likely be waiting a while for Asus to update their driver sets.