Pro logic II turns 2 discreet channels into 5.1 channels.
Pro logic IIx turns 2.0 and 5.1 discreet channels into 7.1 channels.
and then we have Pro Logic IIz
To Mad Lust Envy :
If we set the input to 7.1, and turn DH on, we always get virtual 7.1, no matter what game we play ? [Games could output 7.1 or 5.1 channels]
Remember there is no free lunch. Pro Logic doesnt give you something that wasnt there in the source. If you want the best perfromance with Dolby Headphone, you need to have Dolby Digital 5.1 as the source, NOT pre-processed 2ch Pro Logic.