i asked my mixer (a 30 year pro) that same sort of question a few weeks ago while prepping to shop for mastering houses.

he explained that a "high quality master is a high quality master" and that the best way to have a song translate well and survive the squash to am mp3 is to have it professionally mastered. he further stated that major labels do nothing special to the mp3 versions of their songs other than recording at higher bit depths and sample rates (during the recording process) and ecoding the mp3's at higher 192kbps.

I basically feel the same way. A good master is a good master. If you're mixing and recording is first rate, mastering engineers don't need to do much to it. But I do believe there are good reasons why some folks feel that MP3's don't sound good. One thing that doesn't help is 15kHz television horizontal sync that gets into many recordings. The algorithm has to work very hard to process that 15kHz signal. But I also believe that mastering with some bandwidth limiting isn't a bad idea. So if you bandwidth restrict your material to 50-15,000, you'll probably be doing yourself a favor. You can hear the difference? Big deal. If it doesn't sound good at that response, it can't cut the mustard. Generally, catchup cuts the mustard. So do you like flame grilled audio? Or, fried audio? Tubes are used to keep the fries warm.

Extended response in MP3 doesn't necessarily make that compressed format sound any better. 128 kilobits per second is perfectly adequate for 15kHz bandwidth. I mean if you worry about what every Tom Dick & Harry thinks about your audio? That would be a phalus, see?

10 jumping jacks. Ready? Begin.
Mx. Remy Ann David

SOund

My Space.com sound quality is pretty low, let us say horrible.

Other not so popular sites like audiostreet.net have much more respect to what their members upload in there.