You'd have to play them side by side to see the improvements or supposed. That would be my concern in general particularly film scores. You get the original, the remaster, and hopefully enough new music to justify the hefty price.
Is there an industry standard that requires production to follow? I imagine the whole idea goes downhill if it's recorded too low. I mean if you have new speakers well sure the source (CD) is the best option but why bother with paying more?