The best beginner scope in that price range is one of them GS 6" dobs from Andrew's (
http://www.andrewscom.com.au/site-section-10.htm). They used to be cheaper but at $349, they are still a steal. However if you can swing it, I would go for the 8" dob since it is only marginally more expensive but the views will be brighter (73% more light than a 6"). That and plus the fact that they are both physically the same height and the 8" is only slightly heavier.
Darren