Differences - Sunfire Theater Grand II and III

I believe the major differences are that the III has analog inputs for DVD-A and SACD, and a digital version of the sonic hologram generator, as well as pro-logic II .
There's some other minor differences but I forget what they are.

The II doesn't have 6 channel analog input - honest - if you need confirmation, look on the back for the six discrete inputs. What you're taking about is the DB-25 connector for direct connection [without a bundle of wires] to an external processor or DVD player that has its own processor.
I passed on a II because it didn't have the capability to work with DVD-A / SACD and went with a III.