55 Party: 4way hand with flushdraw

This is the third hand at the table I'm at and the first one I'm involved in.

Party Poker No-Limit Hold'em Tourney, Big Blind is t300 (9 handed) FTR converter on zerodivide.cx

saw flop|<font color="#C00000">saw showdown</font>

Hero (t5099)
MP3 (t6340)
CO (t3112)
Button (t19891)
SB (t22928)
BB (t5435)
UTG (t7670)
UTG+1 (t5193)
MP1 (t8780)

Preflop: Hero is MP2 with A[img]/images/graemlins/spade.gif[/img], 8[img]/images/graemlins/spade.gif[/img].
<font color="#666666">3 folds</font>, <font color="#CC3333">beeny314 raises to t750</font>, <font color="#666666">1 fold</font>, CO calls t750, <font color="#666666">1 fold</font>, SB calls t600, BB calls t450.

In this position, I thought my A8s was good for a raise but I got more callers than I had hoped for.

Flop: (t3000) K[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, BB checks, <font color="#CC3333">Hero bets t600</font>, CO folds, SB calls t600, BB folds.

I think this tiny bet was a big mistake. I believe I was hoping for a miracle and that they would all fold (not thinking), or at least prevent CO from betting big on my flush draw. In hindsight, I think I should've checked it through.

Turn: (t4200) 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets t2000</font>, Hero ???.

I didn't realize it but I picked up a gutshot on the turn. SB has a dominating chip stack and is probably the chip leader of the whole tourney. What's your move here? Any thoughts on the other action?