Supposedly most of the original sound stems were discovered for the '04 mix...most of. That's why you hear a very clear difference in quality throughout the scenes mentioned...most notably in the Tarkin/Leia scene ("..a military target, then name the system!"). Here, the quality shifts mid sentence at times...from the (muddier) quality we are so used to, and the (newly discovered) bits with much greater dynamics. Either many more sound elements were rediscovered, or Wood found a way to equalize them, minimizing the differences because in my opinion, the blue-ray is a far superior mix...with the exception of Obi-Wan's yell, etc.