AK in good sized pot. Check behind or take it down?

[crfergu]

UTG+1 is weak LAG, only seens a few hands shown down and they were questionable holdings. Do I take a stab at it or check behind? Should I have just pushed preflop?

PokerStars Tournament, Big Blind is t600 with t50 antes (9 handed) Converter on pregopoker.com

UTG (t36066)
UTG+1 (t17003)
MP1 (t33444)
MP2 (t10874)
MP3 (t2562)
Hero (t6895)
Button (t17215)
SB (t8565)
BB (t8700)

Preflop: Hero is in CO with K[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/diamond.gif[/img]
<font color="gray">UTG folds</font>, UTG+1 calls t600, <font color="gray">MP1 folds</font>, <font color="gray">MP2 folds</font>, <font color="gray">MP3 folds</font>, <font color="red">Hero raises to t2400</font>, <font color="gray">Button folds</font>, <font color="gray">SB folds</font>, <font color="gray">BB folds</font>, UTG+1 calls t1800

Flop: (t6150) T[img]/images/graemlins/spade.gif[/img] J[img]/images/graemlins/spade.gif[/img] 9[img]/images/graemlins/heart.gif[/img] (2 players)
UTG+1 checks, <font color="red">Hero???