I've just ordered an x-rib 600 / merc opti 135 from Barnet Marine after seeing the boat at the LBS. Personally I think the craft are pretty much a cut price Tornado. If you look at both the Tornado Voyager and the X-Rib 600 on www.ribs.co.uk
you will see that the hulls look identical, as are the centre console, A-frame and tube fittings. Power ratings, hull dimensions and boat weights are also identical.
Having talked to Laurence Lock, Barnet Marine sales rep at the show he told me that the x-rib is built by Barnet Marine and that the hull is built by a major uk manufacturer and that they are built to commercial spec.However, he would not tell me who make the hulls. Also he said that the reason for such a price difference with an identical Tornado is that the X-rib has limited colour choices and the production cost has been reduced. Still looks very like a Tornado to me though, see for yourself!!
6k saving on a tornado of similar spec, and nothing else comes near it for that price!! A lot of boat for the money.
Hope this is helpful. Will post more when I get the boat in the water.