Belles Amp - REL Stereo Subs

Would like to confirm if a Belles 350a Reference amplifier is a "Differential Amplifier" or not. Planning to add stereo REL subs using the High Level speaker outputs to the REL's and REL has specific wiring arrangement for "Differential" amplifiers vs non-differential amplifiers. Having tried several times I have not received a response to this questions from Belles [Power Modules]. Any information would be much appreciated.

Thanks