As above, a really good idea to check the frame out, the price you have quoted is a bit low for this bike, you have to wonder why, a 2008 version should be around the $7K mark not a 2013, you might be one lucky guy but if it was me I would take it to a workshop and have it checked out before you hand over the cash, ask the seller if he is willing to have it checked out, at your expense, if he's not walk no RUN away.
Is a pretty bike tho.