$2/$5 PL with $20 button straddle - KK

[swolfe]

I have K[img]/images/graemlins/club.gif[/img]K[img]/images/graemlins/spade.gif[/img], Villain in this hand has $3.5K and I cover. Villain started out playing very, very tight, but has loosened up slightly since building his stack. He's still probably the tightest person at the table.

I'm straddling on the button for $20. Villain limps for $20 from EP, one other limper, blinds come in, I pot raise $120 more...Villain is the only caller. I've raised from my button straddle probably 5 of the last 10 times.

Flop $360 - A[img]/images/graemlins/diamond.gif[/img]T[img]/images/graemlins/heart.gif[/img]3[img]/images/graemlins/heart.gif[/img]

Villain checks, I bet $200, Villain instantly check-raises to $600, I ???