Total B.S. for suckers. There is nothing to improve on the DCX so far as what is audible by humans according to the known credible perceptual articles dealing with the measurable attributes.
The only worthwhile 'mod' I have seen, and this is certainly not it linked above, is a mod to give the DCX 6 remote-controllable output volume controls, so you can use it as a pre-amp.
-Chris