Mr Lynch has the files, he's adding gossamer wings and fairy dust, or whatever the heck it is that mastering engineers do.

Come to think of it, whilst I was googling recently I came across this Promo/Ad sort of video for a software plugin tool for mastering engineers that demonstrated some of the real sonic differences that mastering makes to your sound.

It's geeky, it's a little technical and a bit 'dry' and will at some point greatly praise whatever software it is he's using (i tuned out soz) but if you want to know what the Mastering process does, it's a good insight.