On the assumption that a 598 has the same 'hidden' options as a 596 then you can set it to output PCM for DD2.0 tracks. Your 568 can then happily process these as DPLII - its how mine is configured. Try:
Open drawer
Press '9' '6' on remote
This should bring up the system menu which has the decode DD2.0 option

Graham

Meridian Owner since 1991