PASSIVE SUBWOOFER DRIVEN by a 2 CHANNEL PRE-AMP + MONOBLOCK ?

Very interesting reading the Nord website. A lot for your money there . Thanks for the recommendation !

Thanks heaps guys . I’ll have to google what is a QSC amplifier and the other recommendations. Much appreciated

yes my Torus 18 inch subwoofer is completely sealed, no ports

I haven’t put a deposit on a Bryston monoblock yet. I only thought of them because after so many friends had their Chinese plate amps fail I thought I’d go with a brand that has a reputation for longevity. But here in Australia Bryston costs an arm and a leg LOL.

Yes my home theatre processor subwoofer XLR out socket can , in theory , be connected direct to a monoblock and then the Wilson Benesch Torus Sub. But the processor has , as one would expect , a global volume knob that adjusts VOLUME of all the speakers plus Sub. 
Auxinput -I think you mean maybe adjust the Trim level in the processor for the sub for a given movie?

i wanted to add a preamp in the chain between processor and monoblock for the sub because some movies have the Bass/ LFE frequencies mastered too loud , other movies the bass is mastered at normal levels. Like in the video world , mixers and studios don’t always adhere to a standard

thanks again guys . I was just reading that even REL has moved manufacturing to China. Sad days.

I just saw the website for QSC amps

seems they do stereo amps  and 4 channel amps

I don’t want to bridge a stereo amp so if I just use the one channel the thing won’t blow up in time ?

I assume they are made in USA - do QSC class D amps have a reputation for longevity ? ( my old Jeff Rowland amps that used the bang and olufsen ICE class D amps weren’t very reliable )

Thanks guys