I know this is going to sound crazy to you but use these plugins, jabos d3d6 1.5.1, schibos audio, and the rsp. however dont enable the send audio to audio plugin.
I just tried the game with and without the rsp and it worked with and didnt without. so that might be your problem.
The game looks great by the way and the sound is ok. a little bit of cracking but not too bad.