Wiring a subwoofer to monoblocks

Just picked up a REL Quake
REL's manual speaks about differential amps – does this mean
Mono blocks?
No friggin idea how to wire it up.
My i/c’s are fibre optics which break the ground between boxes so wiring the earth to the pre is no use.
To make matters worse, the Audiopax reverse polarity /phase.
Have mailed REL but no reply.

When the manual speaks about wiring to the chassis ground,
How do I check this?

Next problem will be a plan to use two subs and I'm not any clearer from their manual how this will be achieved.

I have spare pre outs on the Supratek but would prefer to run the the sub/s using the hi level inputs.
Hi All,
nothing is a problem when you know how!
Big thanks to Jim Smith - I have the knowledge,
all I need now are the connectors/cable...
and another Quake :_)))
Will report back when it's hooked up.
Made up cables and hooked up the sub yesterday.
Not expended much energy setting it up but already I'm over the moon with the results and can't wait to pick up another for a matching pair.
Seems to let the amps really sing, opens everything up and
real bass to boot -result:-)
Thanks for everyones input.
Well this should have been a happy post!
After picking up a second Quake and setting
everything up - sonic bliss.
The two subs were harder to integrate than one, probably due to lack of space limiting their positions I think but the results were way beyond my expectations.
Whilst my amps and speakers were never a match made in heaven, financial constraints meant the subs were my last gasp attempt to achieve the sound I knew the Audiopax could produce.
So after about three years of ownership I achieve nirvana - and two weeks later one of the Audiopax dies:-(
Sometimes I think this hobby is very like the Egyptian Sand dance, two steps forward, three back :-)
All sorted, all singing.
For anyone using lowish powered valve amps with speakers
around 89/91dB efficiency, I'd recommend trying a pair of cheap subs before ditching the speakers.