128Kbs is a very low bitrate for MP3's. An excellent example is the intro to Royal Oil by the Mighty Mighty Bosstones, which consists of a very low level drumroll that quickly builds in volume. At 128Kbs it sounds like noisy digital garbage. At 160 it's recognizable as a snare, at 192 VBR it's fairly close to the original.
In short, there's nothing you can really do, 128Kbs MP3 encoding just does too much damage to recover from, especially when there's heavy pre-filtering done.
/*Music is subjective. Sound is not.*/
