Try
www.myastroshop.com for the skywatcher Dob. You should be able to get it for considerably less than $580. Talk to Bintel about GS Dob. From what I've heard they are abandoning the basic dobs and they are going to stock only premium. You can probably get one from them with a Crayford focuser (well worth the upgrade), and a good set of eyepieces for the price. Either which way you go tell them iceinspace sent you.
The main diff btw the 8" & 10": the 8" you can pick up and carry around easily as a complete unit (esp. after you fit a couple of handles to the base), but with the 10" (and 12") you'd be carrying base and tube separately. And, of course, 10" collects more light, so you'll see more.