Harmy's trilogy and Adywan's Ep1 are reconstructions of an approximation to the theatrical cut. They still contain considerable differences (especially the OT films). Branching from Ep1 Theatrical to the DVD version is possible, as there are less differences than in the OT where virtually all opticals were re-done for the 1997 SE.

I can give you an Avisynth script that enhances Althor's LD rip without losing the unique characteristics of the source (contrast, colour, etc). It's watchable and only slightly below DVD quality.