Call or reraise allin. You If you win this pot you will win else u bust out in third. This is better then finishing second any day.

An initial slowplay flat call of the aces would however been better as u may have drawn in the SB and you had position after the flop on both players.

With 900 in the pot and your weak call SB may have been tempted to make an all-in move which would have been ideal.