DD-EX, DTS-ES, and PLIIx are only applicable if you intend to run 6 or 7 speakers (not counting subwoofer(s)).
DD-EX is simply creating the extra back-surround channels from a DD 5.1 source. DTS-ES does the same thing from a DTS 5.1 source. PLIIx is the 6.1 or 7.1 channel "enhancement" of PLII.
(PLII differs from the original Pro-Logic in that it creates five channel output from 2 channel sources, whereas the original Pro-Logic only created four channel output, with a single surround signal. PLIIx goes one step further by also creating the additional back-surround channels. PLII is a huge improvement over Pro-Logic, but you may or may not place that much extra value on PLIIx.)
H-K's Logic 7 is (I thought) Harman-Kardon's proprietary "equivalent" of PLIIx. Many people seem to like it more than PLIIx, but you will probably view PLIIx as entirely adequate.