It's a little bit of a predicament but nothing that should be a problem really.
Essentially most 2ohm stereo amplifiers are only 4ohm bridged stable (if the amplifier is 2ohm bridged stable your good to go).
With a pair of d2's if you wire them together you'll get a final 2 ohm bridged load on your amplifier (do not do this unless you KNOW your amp can do 2ohm bridged). The problem then is if you can't go 2ohm bridged on that amp the speakers aren't really ideal for the amplifier.
So your left with 2 main choices.
1. Use 1 subwoofer (d2) on the amplifier @4ohm. And not use the other one.
2. Run each subwoofer in stereo @4ohm. This kind of sucks becuase your still not getting the most power you could out of your stereo.
in the event your amp IS only (like most 2 channels) 4ohm mono stable I'd just have the SX's swapped with dual 4 ohm coils if they haven't been used / haven't been recieved and the problem should be taken care of pretty quickly that way.
If your amp can run 2ohm bridged disregard all of the above. Wire it like this.
And enjoy //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
those are your wiring options. you can get 2 ohms into one channel. i have had a few amps that say they are stable to 2 ohms stereo and they were stable at 2 ohms mono. just dont go insane with the gains and test it. run it while watching the amp make sure it doesnt get too hot...... but this is only if you know what you are doing...