Yeah, the sound enhancements don't really do that, even normalize seems to be a bit hit and miss (sometimes i switch between it and volume goes up, other times down!)
It sounds like there's way too much processing of the sound going on. I know the noise cancelling function is software based so wonder if this is getting in the way, as it were? I can find no way to turn it off though.
So without root, it's unlikely to find a solution?