OK - you're interested in DSOs, that means aperture rules. In all honesty, that rules out refractors. Not interested in photography (at least yet) - no real need for a German Equatorial mount then. GOTO is nice, but not strictly necessary. The Nexstar is only 6" - it'll struggle seeing some DSOs imho, especially if from a light polluted city environment. It will making finding them easier though.
I'd personally go the Dob myself. Andrews has some specials at the moment too:
http://www.andrewscom.com.au/site-section-10.htm
scroll down till you find the section named:
Quote:
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Genuine Skywatcher collapsible flex-tube
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The 10" is $899. I'm not sure if it includes eyepieces or not, but you could always pick a few cheapies up that'll last you until you can afford better. I'd recommend the:
GSO 15mm plossl
Andrews 30mm 82º UWA
I'm not too sure what to advise for higher magnifications, the Andrews 4mm plossl that I have isn't very good imho. Maybe the GSO ones are better quality.
Hope this helps.
Dave
edit: get a good UHC filter for DSOs as well down the track