I've just received my XQ30's and XQ centre, looking forward to setting them up at the weekend. My rears and sub are both THX. I'm assuming I would be best to ignore that and allow the auto set up to do it's thing and leave it at that and not set all the X overs to 80 or set the sub to it's THX setting.

Just realised my rears are not THX but my amp is (or will be when I get it)

Personal preference. You can tell MCACC that the speakers are THX and it'll sort out everything except the crossover point. Setting them to 80Hz will bring all the speakers closer together as far as sound is concerned as they'll all be reproducing the same frequency range. You could drop it to 60Hz if you prefer.

If you do two auto set-ups, one where the speakers are crossed over at 50hz, and one where they're crossed over at 100Hz and save them to different memories, you can flick between the two and see which you prefer. Trying 50 and 100 will show a bigger noticeable difference, making it easier for you to choose. If you prefer the 100Hz point, you can either leave it at that, or drop it to 80Hz.

Just remember though that with all the speakers set to small, you'll be listening tp the XQ30's in small mode without the sub when listening in 2 channel mode. To hear them full range, they'll need to be set to large. Unless of course, you want to make use of the sub in 2 channel mode, then setting them to small will be fine as the sub will then be utilised in stereo mode.

Thanks. I want to use the fronts as large so I get the benefit of their full range. Also when watching normal TV/Sky the sub is rarely called upon unless there is a movie in DD, so large should give me a bigger range for general viewing. I'll do as you say and also save a setting without any changes to see what it's like.