I have a REL Storm III connected to B&K M200's. My manual said to connect the ground to the preamp, but I found it works better to connect directly to the amp as Jeff says, EXCEPT - I think Jeff meant to say "With one amp you connect the positive and ground leads and with the other only the POSITIVE."
My amps sit about 6' apart, so I rigged up a harness to them, and connect the REL cable to the harness.