Man, ATs is au-to-matic. His PFR is 30! 30! That's more than most solid players' VPIP. Plus, if he's a good player like you say then, if you 3-bet, there's a pretty good chance of taking the pot on the flop if you both whiff (postflop tendencies are critical to answer your specific question). I'd 3-bet almost any A, any pair, maybe even any two cards that add up to 20, even any suited connector above 67 if I'm feeling particularly frisky.