There has been no indication at any time that the Model 978 will process more than 7.1 channels (with the ability to time align and level match dual subs), nor that it will be DSX capable. I remain hopeful however that the shipping version will include 5.1 plus Audyssey wides or heights capability.

If you want to use PLIIz heights with the 978, you will have to forego using the surround back channels.

Edit: Sorry... I see that this issue has already been dealt with in the other thread. I must admit that I don't stop by here nearly as often as I used to.