Increasingly mid-priced receivers are THX certified, e.g. Pioneer VSX-AX3. My point is do THX amplifiers make non-THX discs sound better? Also, in order to hear the improved THX sound are THX approved speakers required? This is a confusing issue for me. How much better is THX sound over 'normal' dolby digital and DTS? If I invest in a THX amp do I need THX speakers to make the THX processing worthwhile? "Questions...."......."I don't know answers"........"Who does?"