Well, he definatly looks like he's got a hand. At the very worst he has a flush draw (in which case none of this matters). But there's no way in hell he check raises this river on a bluff. not a chance.
That being said, what kind of hands might he check call you with?
AQ,
xh, Qx, KK, maybe even one of those fools with JJ/TT.
What hands are you worried about? AA. I can't imagine him holding any other hand that beats you here.
So what's his play with AA going to be here? probably CRAI. what's his play with any of his other holdings? either check call/check fold.
With all that in mind, I'm value betting here. with $716 in the pot, i want to still be called by any Qx type of hand, along with the JJ's/KK's. You bet too much and you'll both scare away those hands and committ yourself.
So i'm firing $350 on this river. that'll leave you with ~ $600 behind.
Of course, if he does CRAI, i'll puke a bit and then try to convince myself that i need to fold.
I just think this is too good of a situation to pick up what's almost a full extra stack on the river.