MGS has sound problems in ePSXe no matter which plugin you use.
Also it crashes when you meet the darpa chief in version 1.2.0 and you have to use another emulator to change discs when the game asks to.
That's all I can think of,so if you want to play MGS use ePSXe v1.0.1 and make sure you have bleem! or VGS for the disc change.
Or you can only use VGS,it has no problems at all but the graphics are quite horrible(no hardware acceleration).
Hope I helped you.