Sub-Amp Wiring Question - Damping Factor Vs. Power Vs. Bridged/Stereo Mode

8 ohms will give you a lot better dampening. I'd doubt if there is any at all at 2 ohms and the distortion is off the chart too. I wouldn't bridge anything and I would direct couple the drivers to the amp if that is what your trying to do. Get rid of the passive XO and use an active crossover.
 

8 ohms, don’t bridge. So you are saying use one channel of the amp with 8 ohm subwoofer wiring? If so, the problem with that is then I only get 375 watts, which isn’t enough for the subwoofer. I’ve tried it before. Also it’s a sealed design and low efficiency driver so you need some serious watts to get good output.

Bridged implies 2 channels at least.
If that is the case then you could run a 4 ohm VC on each channel optimally.

Hmm… I guess I learned a long time ago that that isn’t a good idea, but for the life of me I can’t remember why. Haha

As long as you balance the channel gains, no problems?

You can run Mcintosh valve amps in series or parallel. Normally one after the other they can't handle low impedance. Paralleled they can half the impedance, to 2 ohms. They sound like crap, but you can do it and that is what Mcintosh recomends..

Using a 4 ohm tap on a SS will give you the highest output with the least amount of dampening and cone control. The lower the impedance the higher the distortion and much lower if any dampening. IF they are using a passive XO only ONE type offers any dampening at all. 6db first order, BUT I guarantee when the impedance goes HIGH the speakers will go out of phase. 

Plate amps and Active XOs DON'T.. 

As I said 8 ohms offers better cone control and can offer a lower octave without a strain. It's a sub it dosn't need watts it just needs controlled movement. Nothing else to compete with so to speak.. WHY a million watts?

I could do it with 100 watt plate amps with cone control.. BUT 1000 watts will blow stuff up if it's not controlled some how.. Just saying.. :-)