i just remember chris mccormatron once saying to me he hated having anything mastered by anyone else cause if it's your track, you want the end result to be the same...... and that sort of stuck with me. you don't want someone fiddling with your own sound. if you truly want to improve your sound, why would you want someone else adding the icing? i think if you don't understand how to master, sure use the expertise of someone like chris, but you need to ask yourself why, and learn it. that's coming from his very own lips... it's a very, very hard science, but it's well worth studying...