As far as sound is concered, there are really only 3 open source sound plugins. The first one is 'No Sound' by zilmar, which won't help is in any way. The second is zilmars 'Basic Audio' which has limited sound, most likely little to no sound within commerical games. Lastly, as I have mentioned, UltraHLE source code.
Yes, UltraHLE was written using Glide. However, the sound is written in DirectSound. As far as porting it to xbox, it is possible. The sound of UltraHLE was already extracted and ported to linux by blight for use with Mupen64. So be optimisic, I believe that if blight can do it Hiraku should be able to do it.