How would you play this? (My first post)

[oxymoron]

PokerStars No-Limit Hold'em Tourney, Big Blind is t20 (9 handed) converter

Hero (t1500)
Button (t1490)
SB (t1440)
BB (t1570)
UTG (t1500)
UTG+1 (t1500)
MP1 (t1500)
MP2 (t1500)
MP3 (t1500)

Preflop: Hero is CO with A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/heart.gif[/img].
<font color="#666666">3 folds</font>, MP2 calls t20, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to t80</font>, Button calls t80, SB calls t70, <font color="#666666">1 fold</font>, MP2 calls t60.

Flop: (t340) A[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, MP2 checks, <font color="#CC3333">Hero bets t300</font>, Button calls t300, SB calls t300, <font color="#CC3333">MP2 raises to t1420</font>, Hero calls t1120 (All-In), Button calls t1110 (All-In), SB calls t1060 (All-In).

Turn: (t5950) A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players, 3 all-in)</font>

River: (t5950) 3[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(4 players, 3 all-in)</font>

Final Pot: t5950

With two calls of my almost pot sized bet and an all-in I was sure at least one of them had an ace-rag to make two pair or flopped a set. I'm shocked I won this and felt like it was a bad call. Thoughts? Typically I don't like risking all of my chips at the beginning of the tourny.