M700's and Rel subwoofers

help, just watched the beginning of the video, and the chap said Rel do not recommend putting a single Rel sub to a pair of mono blocs… what am I to do, I have a few hours until my M700’s arrive. Does this mean I can no longer use the high level connection. As to purchasing another Rel S8/12, due to the UK price, thats NOT an option, as have just bough a pair of M700’s, which will be here shortly (14/03)