4 ohm or 2 ohm subs?

The questions aren't "bonehead".  This forum wouldn't exist without questions, so feel free to ask.

"Rated 850x1 RMS @ 2ohms."   You should say "at 4 ohms".  That's the mono output in bridged configuration.

Amp manual.  Sub manual.

I would choose to use a final impedance of 4 ohms and bridge across the channels for the 850 watt mono output.  Get 4 ohms out of two subs by choosing the 4 ohm DVC models.  With 850 watts of output, each sub gets 425.

As you probably have noted, amplifier output is the same at 1 X 4 ohm mono as it is at 2 X 2 ohm stereo.  The same model DVC subs could be used in either application with some changes in their wiring.   My choice for mono output is primarily because the drivers are in the subwoofer range where the frequencies are so low that the sound is not directional.  Stereo is directional and is therefore not needed in a subwoofer application.

The benefit, if there actually is any perceivable benefit, in running bridged is that each of the subs will receive exactly the same signal.  This correlation of sound out of the two woofers should tend to increase SPL.

The lower frequency reproduction, however, depends mostly on airspace of the enclosure.  At .7 cu ft per chamber you are putting these subs in a box that is on the small side.  You would likely have a noticeable increase in the low end response if you provided these subs with 1 cu ft each.  Whether you power the subs in stereo or mono takes a back seat to providing the best air volume in which they will operate.  I recommend that you buy one pound of Acousta-Stuf and divide it equally into the two chambers to increase the apparent air volume.

Yes.  I posted a link to the diagram above.  And you're welcome.  Good luck!