KK vs. AK

NL TEXAS HOLD EM $10+1

I dont have exact chip stacks but this is close

Villian 2000
IRSdude 2200

** Dealing down cards **
Dealt to HERO[ Ks Kc ]
HERO raises [400].
dragon5_us folds.
LazyAssWilly folds.
santy_claus folds.
IRSdude calls [300].
** Dealing Flop ** [ 5h, Ac, 9h ]
IRSdude checks.
HERO bets [400].
IRSdude calls [400].
** Dealing Turn ** [ 5c ]
IRSdude checks.
HERO bets [400].
IRSdude calls [400].
** Dealing River ** [ 7c ]
IRSdude bets [800].
HERO is all-In [663]

Is this to aggressive to play kings verse the chip leader?
Should you check an ace on flop?
is that a good call because pot committed?

The subject is not correct for the way i posted this hand. IRSdude was playing ace king though