I didn't dare to react to baldr's post, but my brain froze for a second when I read it.
acoustic or digital, the guy mastering the album listens to it on speakers(or at times headphones). so of course this guy knows what everything sounds like, it sounds however he wants. ideally if we wish to know what anything should sound like, we must all listen to the album with his equipment in his room when he's finished the album, and not pretend that we know because we've heard the band live or because we played the guitar. that's irrelevant, the product we have as reference for fidelity is the final master, not the live performance.
You forgot a couple links in mastering engineer's audio chain...
his ears and
his brain.
Unless, of course, everyone's ears hear exactly like his and their brains interpret the sounds exactly like his as well!
So to my way of thinking, the science (i.e. measurement/fidelity) aspect of this really only helps to establish a sort of baseline which a lot of high-quality gear these days can achieve or surpass. In many objectivists' minds that serves to reaffirm that any equipment over pick your price-point/measurements/etc. is a waste of money. In many subjectivists' minds, there are a variety of valid reasons to spend more money whether it's better sound/equipment quality/brand/self-esteem/etc.
I take a blended approach that serves my preferences well; meaning that I'll pay a slight premium (i.e. $600 vs $200) for design concepts/customer support/etc. that make sense to me. Currently for me, Schiit is a leader in this market largely because of their overall approach...
Oh yeah, and I also like the way my music sounds through their stuff. Is it MultiBit or is it Memorex?