try using bbe's sonic maxximiser. but use it spareingly!!! it will help put a little bit of a shine back onto the track and then use a peak master on it to bring it up to a level of about -1. a louder track can fool the ears into thinking its a better production. you'll never undo the compression that occured when you rendered it to mp3 but if you only plan on playin it in loud clubs you may well get away with it if you doctor it up a little.