Blind v Blind, A-high flop

No arguments to raise preflop please.

Bodog 7.50. I'm big stack in the tournament with t85k. My image is tight. Blinds t800/t1600 with t150 ante. No read on villain, which usually means tight.

Folds to villain in SB.
SB (t23k) completes.
Hero checks with T[img]/images/graemlins/spade.gif[/img]7[img]/images/graemlins/heart.gif[/img].

POT = t4k
FLOP: A[img]/images/graemlins/heart.gif[/img]T[img]/images/graemlins/heart.gif[/img]9[img]/images/graemlins/spade.gif[/img]

SB bets t4k
Hero?

In addition to how I should play this specific hand, what do you typically think when the SB completes and leads an A-high flop?