Several of you have contacted me re effects of front speakers with / without THX mode engaged and what it does. So for Stewart C, Johno and a couple of others, this is my thoughts on this. The basic question asked? Is there a difference in sound quality that comes from the fronts when you engage THX Cinema mode? THX is a set of standards that I generally buy into. They are divided into several areas and I need to explain what they do / their effect. Fuller / better descriptions are elsewhere, like THX web site. Others will no doubt have more time than I to explain THX in detail. THX Power amps Basically I dont buy into this one at all so I will leave it at that. THX Processors / Receivers At its best with PL sources. They performed de-correlation and re-equilization. The first makes mono rears different and the second tames the treble in the smaller domestic environment. (Most sources, until DVD, were mixed for the cinema only. Now days this has changed.) THX Speakers Special crossover characteristics and dispersion (for treble) needed for the front speakers. For rear / side duties di-poles were recommended. In the heady days of ws VHS and laserdisc then THX was brilliant. It really addressed the problem. Now days with re mixed digital DVD signal, its use is less obvious. The advent of multi channel music has cause THX some problems. The dispersion characteristics that were so good for PL films, now works against it. THX has been around for 10+ years now. Pressing the THX button on your receiver will alter the amount of treble (re-equilization) going to the L, C and R speakers. However if the speakers are THX badged, it also means that there are some quite unusual dispersion characteristic that arent the best for music (but brilliant for movies). This is why many of use conventional speakers for L, C and R and THX di-poles for rears. Many loudspeaker designers have already realized this and therefore dont send their speakers for certification. THX has realized that there is a problem and therefore have THX2 Ultra specifications which eases these movie based requirement gearing the speakers more to both movies and music. It is a welcome development IMHO, I have yet to hear it in practice however. That is why KEF market a THX kit, that is awesome for films. However for those who like stereo and multi channel music as well then the Ref L and R speakers are best matched with the Ref Centres (100 and the cool 200c) and then add the THX di-poles for the rears. Different speakers for different markets. People need to decide what they want to use their kit for. THX certification is therefore a two edged sword. You need to know the pro and cons. Anyone else like to add anything?