Having THX ReQ is not the same thing as being THX certified?

Some non certified receivers have the ReQ processing, which rolls off the high end so the soundtracks aren't as bright.

Being certified has to do with more processing, (decorelation, and bass management, and power handling per channel) as well as a certain build quality.

Having said all that, I agree with Mike B that it is worth the cost. Check out their site for the specs on certification. They probably list the products that have it.

Will you be able to hear a big difference? I would say that you're going to have to first deal with the move to full discrete surround first. That is a big difference.
But having viewed over 350 DVDs in my system, that yes there is an audible difference.

Take your favorite discs and go listen for yourself.

Paul