Five Diamond $1.5K: TPGK facing raise on flop

[Todd Terry]

20 minutes in, 25/50, I and Villain have about 2500 chips (started with 3K). No significant hands have been played by either of us, he gives the impression of knowing what he's doing. I raise UTG to 125 with AdQs, Villain calls in CO, button calls, SB folds, BB calls.

Flop: Ac 7c 7s

I bet 300, Villain makes it 800, other 2 players fold. Hero?