$25 Home STT: Bottom set in BB vs huge stack and loose passive

Looking for any advice about my line or alternate lines.

6 players left out of 9
Blinds at 50/100. 5 minutes left until 75/150.

Big stack is UTG+1 with approx 6000 chips.
There's a loose passive OTB with approx 3000.
Hero on the BB with 2300.

Big stack definitely knows how to play well and has been bullying the table. So far I've only played 2 hands in the tourney. Button called off about half his stack vs. me earlier when I had AA. I don't think he remembers that hand though. UTG+1 is aware that I have been playing tight most of the night.

Preflop Action:
Hero has 6[img]/images/graemlins/heart.gif[/img] 4[img]/images/graemlins/diamond.gif[/img]
UTG folds, UTG+1 limps, 1 fold, Button calls, SB folds, Hero checks in BB.

Flop: 4[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/club.gif[/img]
I'm pretty sure UTG+1 is going to bet this pot. I think Button will ride along with a wide variety of holdings. The two [img]/images/graemlins/club.gif[/img]'s on board make me want to end this hand well before the river so my plan is to check-raise.
Action:
Hero checks, <font color="red">UTG+1 bets 400, Button raises to 1000</font>, <font color="blue">Hero ???</font>

Here's where I started to doubt a little. The only hands that beat me are KK or a better 4. I'm pretty sure Button doesn't have either of these, so I figure him for a K with middle kicker or the flush draw. If I stick with the original plan, this is an all-in for me, UTG+1 will fold, but now Button will probably call.

Alternate line that I was considering: Call off the 1000, hope that for some inconceivable reason UTG+1 will throw more chips into the pot. Then auto-push the turn, while being prepared to puke if the turn is a [img]/images/graemlins/club.gif[/img].

Let me know what you think Hero's line should be here.