Do you run everything from the unbalanced RCA in and outs or, both, balanced 1/4” and unbalanced RCA’s. The manual says that “The diagrams show both balanced and unbalanced connections, but for each channel you should use only one or the other."
My REL’s only have RCA inputs but it doesn’t make sense to use a balanced XLR cable with adapters, or have a custom cables made up with 1/4” TRS-style connectors on one end and RCA’s on the other.