Here's my idea:
- Connect your DVD to the TV via a component (not composite) video lead. Set your DVD to output video, not RGB or S-video.
- Connect your ntl box to an RGB-enabled scart socket, via a scart lead. Ensure the ntl box is set to output RGB, not composite.
- Connect your X-Box to an RGB-enabled scart socket via a scart lead.
I don't know how many RGB scart sockets your TV has, however if it doesn't have enough, invest in a quality scart switcher, e.g.
JS Technology Master Scart Controller.
Regarding leads, personally I wouldn't spend too much. I've gone for, relatively cheap, Belkin PureAV leads, which are available at dabs.com:
http://www.dabs.com/uk/Search2/resul...hPhrase=pureav
An offical X-Box scart lead should be good enough, although there are lots of (expensive) alternatives.
I'm sure other people will come up with their own recommendations though.
Can't help you with your speaker problem. Good luck.