Music Res Question

I was watching Skyfall on BluRay via my mid range 7.1 system and the theme song in HD (certainly the vocals) sounded much better than the 256k file I listen to via my Superuniti and Kudos S10 speakers.

I guess my question is - is this normal or has that song been mixed differently to accentuate the vocals?

And if it is normal then why we don't we have BluRay quality Albums? FWIW I have a few HD albums inc some that I also have on CD and I don't hear the same difference that I heard listening to BluRay on my home cinema system vs CD (or less) quality on my dedicated stero system.