S.T.A.L.K.E.R. Clear Sky - 5.1 Surround Sound Enabler:

1- It should be compatible with any mods.

2- To enjoy surround sound, make sure that you have OpenAL, that renders 3D sound and is compatible with S.T.A.L.K.E.R, installed.

3- Copy and paste "bin" folder into your game dir, overwrite files when asked.

4- Start up the game, there should be a new sound device showing up in the sound settings menu, called "DirectSound". Select that, enable EAX and restart the game.