Get the 10" GSO dob from Andrew's period (to Brissie it only cost about $650 plus postage). You won't regret it. I find the 10" straddles the price range and portability just nicely. The 10" fits easily in my Hyundai Excel Sprint with the seat down. I don't think the 12" would fit in. Also I find I can carry the whole setup (yup tube plus mount) for short distances although I would not recommend that you do that often
Darren