Bridging NAD 3155 and 2155 to include a subwoofer

atyourkitchendoor, I assume you know how to bridge the 3155 and 2155 to make them into 2x125W with a pair of Y adapters and connect to the super 8. With this configuration, your super 0s will be running at full range. 
the other option is using speaker level connection and high pass the super 0s.

Yes, If using birdged configuration, y adapters is the only option.

Just want to clear things up and not to offends anybody,
https://www.amazon.com/dp/B0049FGP7O?_encoding=UTF8&*Version*=1&*entries*=0&showDetailTe...
above  information shown the speaker level output on super 8 do has a built-in 100Hz high-pass filter.
If 3155 and 2155 are bridged, the amp output will be floating from ground and should not connect via speaker level input of the super 8 that has common ground on both R/L negative connections.

Totally agreed, thanks