My experience with PCs has been transport first, then preamp. I think my two DACs (Cambridge IsoMagic, Apogee DA-100E) were unusual, because most often I have heard that the DAC is the first priority. For mine, though, very little difference.
Power cable hierarchy for components
I realize that there are no definite answers here BUT I'm curious as to what you're thoughts are on inserting high end power cables on various A/V components. Which components do you feel would yield the greatest sonic benefits by adding a high end PC and in what component order would you add them? Various threads on A'gon seem to suggest that digital components are the way to go yet some of the companies I have dealt with push the Amp's....any thoughts?