a FiiO E12 won't be noticeably better than the ZxR, you need to go a bit more upmarket than that.
Do you use the "Bass" and "crossover freq" settings thing in creative software "SBX pro studio" ticked ?
untick if you have ..... it does the same to me and its rubbish feature don't use it, I've tried a few headphones and farts bass with all of them.
Or maybe my sound cards faulty![]()