my second hand at the table

Party Poker 10/20 (6max, 6handed)

Preflop: Hero is SB with Q[img]/images/graemlins/club.gif[/img], T[img]/images/graemlins/club.gif[/img].
UTG calls, Button calls, Hero completes, BB checks.

Flop: A[img]/images/graemlins/heart.gif[/img] T[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/club.gif[/img]
Hero bets, BB folds, UTG folds, Button raises, Hero 3-bets...

Too aggressive vs. unknown? If so, what's my line?
What if the top card was a king instead?