AK hand, too aggressive on the river?

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Party Poker 0.50/1 Hold'em (10 handed)

Preflop: Hero is SB with A[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/spade.gif[/img].
<font color="666666">1 fold</font>, UTG+1 calls, <font color="666666">3 folds</font>, MP3 calls, <font color="CC3333">CO raises</font>, <font color="666666">1 fold</font>, <font color="CC3333">Hero 3-bets</font>, BB calls, UTG+1 calls, MP3 calls, <font color="CC3333">CO caps</font>, Hero calls, BB calls, UTG+1 calls, MP3 calls.

Flop: (20 SB) K[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/spade.gif[/img], 8[img]/images/graemlins/heart.gif[/img] <font color="blue">(5 players)</font>
Hero checks, BB checks, UTG+1 checks, MP3 checks, <font color="CC3333">CO bets</font>, <font color="CC3333">Hero raises</font>, BB calls, UTG+1 calls, MP3 calls, CO calls.

Turn: (15 BB) K[img]/images/graemlins/club.gif[/img] <font color="blue">(5 players)</font>
<font color="CC3333">Hero bets</font>, BB folds, UTG+1 folds, <font color="CC3333">MP3 raises</font>, CO calls, <font color="CC3333">Hero 3-bets</font>, MP3 calls, CO calls.

River: (24 BB) 9[img]/images/graemlins/spade.gif[/img] <font color="blue">(3 players)</font>
<font color="CC3333">Hero bets</font>, <font color="CC3333">MP3 raises</font>, CO folds, <font color="CC3333">Hero 3-bets</font>, <font color="CC3333">MP3 caps</font>, Hero calls.

Final Pot: 32 BB
<font color="green">Main Pot: 32 BB, between Hero and MP3.</font>