I tend to always go with my gut in situations like this. I remember when I played GUKPY Plymouth last year, first big comp I bought in myself for (ie no satellite seat). And I busted out with KK vs AA in the first level. I felt sick, not because of the money, but because I knew the guy had aces but I still didn't pass. I knew preflop and didn't pass, and I knew on the flop, and still thought moving all in was a good option....
A month later, I was playing a £50 stt in my local. I make it 400 to play with KK, BB makes it 2000 to play...I know he has aces. I think for ages then pass and show the kings face up, and he shows me AA. Now why can I make a lay down like that for 50 quid, but not for 1000?? Probably because it stung so much at Plymouth. It's a good lesson to learn, and I'm sure next time, you might just go with your gut.
You knew because you've played against him before?