I freakin hate myspace. The streams always sound so poor no matter what kind of music.
But anyway, a lot can be said about the effectiveness of filters, High-Pass and Low-Pass. If a source for recording and/or mixing needs any sort of EQing the first thing I will reach for are the filters. Almost always things sound out of place because of too much high, or too much low-end.
Harshness can usually be remedied by using a low-pass filter on a really gentle slope (6db/octave). And listen to the source in the track and slowly sweep down until it starts to sit in the right place. The Kjaerhus GEQ-7 has very flexible filters as well as 5 band parametric EQ. One of my go-to plug-in EQs.
By the time I'm done a mix, whether for rock, or hip-hop (i.e. live recorded music or sample-based), one out of two tracks will be employing a filter of some sort.