Considering the final end result is still a 44kHz, 16-bit audio CD, the source could be from a much higher resolution but is there really a perceptible difference? In the case of the previously mentioned Titanic album....nope. Can't say the same for any other K2HD release, though.
I broke down and bought the K2HD version of TITANIC mainly for the nice book it comes in, I haven't listened to it yet, I'll let you guys know how it sounds soon.