THX certification is a set of different standards that manufacturers meet and pay a certain sum for the right to use the logo. There are features that I personally disable to make the sound better. The Re EQ function is only used when the movie has been subjected to what is known as an X curve eq. I believe this is done to compensate for the size and acoustics of theaters and make the sound more natural sounding. In the home environment, this makes the sound worse as we don't need such emphasis. The Re Eq function is great for such purpose. This might be the reason why THX receivers sound muddier because of the lack of high frequency. Most DVD and HD sources are authored for the home environment ,therefore we don't need the ReEQ engaged.
