Btn - $7000 - Somewhat thinking 42 year old player that plays something like 40/15. He is more on the good aggressive side, but still has a lot of leaks like most Live players (like limping in too much).
BB - $2500 - AsQhThTd

2/5/10 with mandatory button straddle

Preflop:
Sb folds, Hero raises to $20, 2 callers, Btn calls.

Flop: KcQdQs ($80)
Hero checks, 2 checks, Btn bets $40, Hero calls $40

Turn: 7d ($160)
Hero checks, Btn bets $125, Hero calls $125

River: Ac ($410)
Hero checks, Btn bets $300, Hero???

As played, villain can definitely have weak KK here and some AQ as well. Its hard for me to find a bluff though. It would have to prob be some random weak Kx hand. After we c/c twice, I think our range looks pretty strong. LIke Qx+, AA:dd. So I'm not sure how often villain will actually follow through with a bluff. Would you guys call or fold here?