Just a quick note here, though you haven't actually gone quite this far in your discussion:
if you do go buy an external equalizer, don't use it for any home theater feeds between the DVD player and the receiver. The decoder in your receiver is looking for certain aspects of your signal, and if you change these with an equalizer before the signal gets into the receiver, the decoder chip may fry itself trying to re-correct.
The external is fine if you are running a source to a "Pure Direct" or other circuit that doesn't engage the decoder chip.