I ride a 2002 super galaxy, identical model to the 03. For the money it's pretty much unbeatable. The new model is a compact frame (sloping top tube) and the 853 a lighter and probebly stiffer material. Thorns use the same material but mostly use a smaller wheel, which is more universal if you plan to tour the world - spares etc.
If you are planning to stay in Europe then I wouldn't worry. The Super G comes with all racks and guards, STI shifters and is an incredibly comfortable bike, the tyres are chunky (32mm) and bullet proof and most of the equipment is mountain bike stuff, built to last with minium up keep. If you go for the Dawes then the money you save could get you completely kitted out with panniers and all other creature comforts.
The Super G has slightly gone out of fashion as Dawes were going through various take overs etc and took their eye off the ball for a few years while the competition caught up. Thorns use practical the same gear but are way dearer. Another company that has won 'Best Tourer' for the past 2 years is Hewitt. These are handbuilt frames, the geometery, as with Thorn, are different from Dawes and may be lighter, but if you are using it for a fully loaded tour then you may not notice.
http://www.hewittbikefitting.co.uk/
The Super G is still exceptional, for £600 it's an awful lot of bike for the money. Thorn and Hewitt are built in the UK which probably account for the higher price (dawes now built in Far East), with Hewitt you will get measured and the frame built specifically for you. Hewitts start at about £899, Thorns maybe a bit more.