Yes, DPLII extracts the surround ambience from the front channels and sends it to the side surrounds in a 5.1 speaker setup.
DPLIIx can be applied if the speaker setup is 7.1. 2-channel material has the ambience sent to the side surrounds plus ambience which is about equal in level on both sides is sent to the back surrounds for imaging there. 5.1 material where there's discrete side surround content in the 4th and 5th channels is processed by DPLIIx so that content about equal in the side surround channels is extracted and sent to the back surrounds. The front channels in the 5.1 material aren't processed at all, because there's already surround material in the discrete side channels.
