I found some pertinent info re the Powernode2i; I didn't realize it had this degree of subwoofer control. From Bluesound support:
"The POWERNODE 2/2i is roughly 120W at 4 Ohms or 240W at 2 Ohms.
The MQA Decode only happens on MQA Files - Non MQA Files do not include MQA requirements. Filter is really not the right word you are looking for - please see
www.mqa.co.uk for more details.
Analogue inputs are not a pass through, they are converted to 24/192 via a Burr-Brown ADC with a >100dB signal to Noise ratio.
On the POWERNODE 2/2i, directly connect the SUB-WOOFER to the Player using a Sub woofer cable to the sub out. On the VAULT 2/2i or NODE 2/2i, it depends on the Amp used and how you are controlling the volume.
The SUB port is always active, but with SUB-WOOFER On then all <80Hz frequencies are diverted from the mains so you can drive them..."
Granted this is hardly Kal Rubinson level subwoofer integration, but it's damn handy for audio-amateurs like myself. and btw, if this OP wants a superb description of integrating a subwoofer into either 2 channel or multichannel I advise a read of Kal's review of the JL 110v2 sub in Stereophile
https://www.stereophile.com/content/jl-audio-fathom-f110v2-powered-subwoofer