Pushing with top pair? ($11)

[Huckle]

Total number of players : 4
Seat 10: Hero, BB ( $970 )
Seat 5: UTG ( $600 )
Seat 6: UTG +1 ( $4670 )
Seat 8: SB ( $1760 )
Blinds(100/200)
Dealt to Hero [ Q[img]/images/graemlins/spade.gif[/img] 9[img]/images/graemlins/diamond.gif[/img] ]
UTG folds.
UTG +1 calls [200].
SB calls [100].
Hero checks.
** Dealing Flop ** [ 5[img]/images/graemlins/heart.gif[/img], T[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/club.gif[/img]]
SB checks.
Hero is all-In [770]

Is this a no-brainer or is it better to just push preflop? The bigstack had been limping a lot all the game with anything, and couldn't really be put on a hand. SB might have anything, probably a weak ace or low pair.