[M.B.E.]

A_Plus, I think you're right that raising the flop is in order. It's a little counterintuitive because our goal on a flop like this is to get all-in multiway -- that's much better than getting all-in headsup (which is why most in this thread wanted to call the SB's bet). I'd prefer raising to 275, not 300, but not a huge difference there.

If we just call the 100, there's a good chance the other two will call as well, then on any non-club turn SB will push his 520 into the 520 pot. That is generally a disaster for us with the straight flush draw.

You didn't give the payout schedule. It doesn't really matter to this particular decision, I suppose.