I check this flop. Then based on the size of MP2's continuation bet (assuming he makes one), and the action of the other players after him, I'll probably be in a better spot to make the correct decision. I don't like betting out 300, because you give MP2 a chance to fold any hands that you have beat, while allowing him to extract extra value out of the hands that are beating you. Also if you get several callers you've put yourself in a real tough spot on the turn. On the turn in the actual hand though, the 9 is actually a great card for you, as it makes it less likely that someone else has it.