Albert, thanks also. I realize that. In this case, however, the tradeoff appears to be between (a)connecting at speaker level, which would require soldering a wire onto an RCA plug, for each channel, and (b)connecting at line-level, which would require purchasing additional interconnect cables, possibly purchasing splitters and introducing them into the signal path, and possibly spending several hundred dollars or more on a buffer, while losing the possible sonic benefit of providing the same signal to both the subs and the main speakers, and introducing the possible sonic effects of the splitters or buffer, if needed, and of the additional interconnect cables (which for several reasons I would expect to be more significant than the effects of the Neutrik cable).
Understood, my point was operation with a buffer (Bruce obviously already owned) helped resolve an issue.
Such as In my case, where the JL Audio subs required interconnect cables, unlike the REL which probably works better as designed from speaker terminals.
In my case the subwoofer dragged down the bandwidth of the main system when both sets of interconnect were used.
In cases like this, the buffer saves the day. Literally, only other options are to sell the sub or suffer serious loss of bandwidth.
I don't question the wire suggestion you made for the REL.