100NL: We hit gin, but should we check behind on turn?

[SirFelixCat]

Villain is a pretty weak 25/16. Obv. not a reg, but not a total monkey either. I've yet to see him get out of line at any point and not sure how he plays his draws, but know he's folding a weak K on the turn to heat. So how best to maximize?

And I would have 3bet this pre had we not had a TOTAL monkey right behind me that I wanted to come along for the ride, pre.

Full Tilt Poker, $0.50/$1 NL Hold'em Cash Game, 6 Players
LeggoPoker.com - Hand History Converter

BB: $92.60
UTG: $39
MP: $127.10
CO: $122.15
Hero (BTN): $150.85
SB: $132.40

Pre-Flop: 9[img]/images/graemlins/club.gif[/img] 9[img]/images/graemlins/heart.gif[/img] dealt to Hero (BTN)
2 folds, <font color="red">CO raises to $3.50</font>, Hero calls $3.50, 2 folds

Flop: ($8.50) 3[img]/images/graemlins/spade.gif[/img] K[img]/images/graemlins/spade.gif[/img] 9[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">CO bets $6</font>, <font color="red">Hero raises to $21</font>, CO calls $15

Turn: ($50.50) 3[img]/images/graemlins/diamond.gif[/img] (2 Players)
CO checks, <font color="red">Hero ???</font>

Since we raised the flop, we very well could have a FD here or a set or a K or or or...

The question here is what does he put me on and if I check behind (fd), I can probably get a bet, if not more, out of him on the river. Plus, if he has a draw, he is surely going nuts on the river. But, would he call a bet on the turn w/ a draw? I KNOW he's not w/ a hand like KJ etc, so do we bet or check behind having a virtual lock on the hand?