It’s not a matter for REL to decide, it’s a matter for Naim; as, depending on the cable used and the type of Naim power amp you could actually damage the power amp by connecting an inappropriate load to it.
There was an FAQ on the old forum site but this doesn’t seem to have made it onto this forum’s FAQs; however this gives the electrical spec of the load required for Naim amps…
You will need to ensure that the combined load of the two cables still meets these specifications, otherwise you’ll degrade the performance of the Naim amp, and could possibly damage it.
Connecting to the back of the speakers will ensure a safe load for the amp.