Since you don't give enough info on the amp, I will assume the amp can only be loaded with 4 ohm bridged. Since the sub can't be wired for 4 ohm, you have the next best thing which is 8 ohm - http://i81.photobucket.com/albums/j230/sparky3489/SERIES-DUAL.jpg
This will only make the amp push half the power for a 4 ohm load bridged.