How are you currently wiring your subs to your amp? I don't quite know what a bridged connection is, but I do know the crutchfield diagram is the wiring you would want to use, since it provides a 2 ohm load to your amp at the sub's rated 250watts.

What kind of box are they in?

Also, 10 gauge might be a tad bit overkill for speaker wire; I used 12 gauge for a 750 RMS sub. I hope you are running a decent gauge power wire (at least 4) and have the appropriate fuse.