Using a REL Storm with a Spectrum Amp?


I have a Spectron Musician 3SE Mk2 amp and I have been using full range speakers. I am demoing a set of monitors and an REL Storm III sub. Does anyone out there see any problem with running the sub by using a Neutrik NL4FC cable from the sub to the terminals on the Spectron...where the the positive and negative leads would be connected to one side of the amp speaker terminals and a single wire connected to the negative terminal on the other side? Just want to make sure all components are protected!
128x128mdrummer01
Why wouldn't you just connect the sub to the preamp outs and not worry about possibly shorting the amps outputs?
Rwwear: The Neutrik option is one of two, the other being a Y connection from the RCA preamps out. The difference is the Neutrik cable is way longer and allows more placement options for the sub than the preamp-out option.
I don't quite understand why you would want to connect the extra wire to the negative terminal. The positve and negative wires will be connected to their respective counterparts on the amp?