The multi-state DS rides have me thinking of the 650 Honda, but the enduro racing points to the 250's. The 400 might be the compromise you need. If you plan to truck the bike to your various DS rides, the KLX would be my pick.
I am roughly the same height/weight as you, and use an XL600 as my trail/DS bike. It feels light compared to my Dorsoduro (which I also ride off road), but I don't think I would be remotely cometitive in an enduro race with a bike that big.