I think Pauls gauge is of great use, even without the sounds. By this, I just wanted to drop that he may have no control over the dsd_fsx_xml_sound gauge development as that's from another author (Doug Dawson). http://library.avsim.net/esearch.php?CatID=fsxgau&DLID=158634
Don't worry, it's meant to be used by other talented developers like Paul. It supports FS9 and FSX. And the idea, the concept on the 737 and the sounds are all from Paul.

The differences between FSX and P3D aren't that big, so I doubt that huge problems cause the incompatibility. It may just be the version string or the wrong name of the flight sim process to trigger such no-go events. As I saw, it uses Simconnect and, as P3D features a slightly different version, may fail to initialize or find the spot to actually start working.

Well, you can write the author if you like.