major hand late in large multi -- daniel help???

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Here's the situation:I've been around the block, and have made many final tables in large multi-table tournaments online... but this hand really had me thinking for a while...I'm in 5th or 6th out of 60 or so players left in a $10+rebuys tournament, having been in the top 3 for most of the tournament. I'm really in the zone and playing my A game. Top 27 get paid.I have 49,000 chips, Villian has 38,000 chips, and he's one of the players I'm trying to avoid getting involved with. Blinds are 400/800.The Villian limps from EP, I am the only other caller w/ 5s 6s on the button.The flop brings Ad 7s 8s. The Villian bets the pot (about 4500). I think for a long time and finally decide to push all in. Unfortunately he calls w/ one of two hands I *really* don't want to see, As 9s (the other is As 4s).I have my own thoughts on whether I played the hand correctly or not... by the way 27th pays $66, 1st pays $3k, top 3 is at least $1k... I was curious as to your opinions, especially Daniel's (obviously).Oh -- I lost the hand, and busted out on the bubble :cry:

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Additionally, he seemed to be a very careful player -- I would not have made this move against an obviously loose/bad player. (i.e. I thought I had decent odds of taking the pot down on the flop)