I just received my Onkyo TX DS989 upgrade with all the new goodies. I was wondering, what is the best surround for a dvd? I'm sure it's up for interpretation, but between Dolby Digital EX, THX Surround EX, and THX Ultra 2, what is the better surround to use for a dolby digital encoded disc or for an EX encoded disc? Any advise would be appreciated. Thanks!