SNAPSS is, eventually, hopefully going to add custom hiteffect sounds. Unfortunately the engine uses the same sound - and entity - for both "impact" and "explosion" events. Thus a great big shell hitting the armor will sound the same as a big explosion.....which is bad sound design as it doesn't provide good aural feedback about what's happening. While this would likely be troublesome to change, cloning the armor hit sound and using a different means to define the sound of an explosion (fragmentation) event would make life a lot easier for SNAPSS, and also allow more hardcoded sound-design in mods.
Basically we need the engine to handle things differently so that it doesn't overlap. It may be possible for us to work around it, but ideally it'd be a 1.8 engine fix.