Another new feature is the furthering of IV transfer. Previously, when the parent Pokémon had power items attached, it guaranteed the transfer of one of the IVs, while several IVs were guaranteed to pass down. However, as of X & Y, if you have one of the parents hold the Destiny Knot item, then 5 IVs total from either parent will be guaranteed to be transferred
Therefore, the Destiny Knot can make the parents pass down 5 IVs to the offspring.
To confirm your query, they don't pass down the highest IVs, they can still pass down the x IVs. Did you know that? Or am I missing something? xD
Hope I helped. :)