I'm going to go against my better judgement and try one more time gcmarshall,
I honestly don't think you've tried to understand a word that has been written to try and help you. Although I can accept that perhaps you can't appreciate the THX certification difference, and you are not alone.
THX certification is part of the electronics design and equipment performance no matter what sound mode you are in, not just when using "THX Cinema". The main point of THX certification, as has already been said numerous times, is that it guarantees a certain level of HT performance excellence, Ultra being more demanding than Select.
By participating in this "Good Housekeeping Seal of Approval" rating system, manufacturers can assure customers that they are getting a performance excellence, "Ultra" being more demanding than "Select". The "Ultra" family of certifications indicates excellence in performance can be achieved for large HT setups (up to 3000 cu ft listening rooms) while the "Select" family of certifications indicates excellence in performance for smaller HT setups (less than 2000 cu ft listening rooms).
The "Select2" & "Ultra2" designations are applied to receiver & amplifier equipment, while "Select" & "Ultra" designations are applied to speakers , DVD equipment etc. The "Select, Select2" & "Ultra, Ultra2" families of equipment are "complimentary" and work well together at their respective levels of performance.
Many will argue they hear no difference between THX certified or non-THX certified equipment. Many will argue that THX certification just allows manufacturers to justify raising the price of the equipment over competitors. Some will argue that the showroom salesman knows which equipment performs best. I'm sure the lack of transperancy in the THX standards makes certification suspect in some people's minds.
But in spite of everything, nobody can argue that THX certification "attempts" to quantify HT performance in a measurable way. It is, however, merely a tool. Maybe audiophiles don't need this tool, or say they don't, but many of us mortals can use all the help they can get. Personnally, if I see two units with the same features and claimed performance I'm looking for and only one unit is THX certified I'll buy the certified unit because I know that an independant party has verified that it does what it claims.