Well, any errors introduced in an initial DAC step won't be recovered later on so performance isn't irrelevant. Better to send a digital signal to the monitor if possible though.
As far as I'm aware there is no reason that exactly the same can't be achieved using subwoofers, with their various advantages over larger main speakers.
I'm not sure it's actually possible for you to cancel your order even if you wanted to. I think all the Bluesound Node has is basic tone controls though? If so it's not remotely in the same league when it comes to managing bass room resonances.
This thread is about the Flex so I was referring to its manual, and specifically in the context of Dirac Live. You can get digital clipping with a 2x4 HD as well though, it just comes down to the input signals and filters used. There is no automatic headroom introduced by miniDSPs, which is good...
There is no 'analogue part' - it's a purely digital volume control. People do complain of digital clipping being an issue on other miniDSPs if the volume is left at 0 dB. I bet the Flex manual includes a warning about this.
It's a digital volume control so you can easily leave it at a fixed value but the 0 dB suggestion above may be too high if filter boosts are applied as this could cause digital clipping.
The cheaper 2x4 HD and DDRC-24 models don't have a volume control knob if that was part of the issue, but...
I know nothing about Linux support but for info. with the SHD it's possible to see the USB return signal using REW and setting the SHD as an input device as well as an output. On the miniDSP forum I've seen someone posting about having done the same with a Flex.
The question is about the USB output though.
@mike70 has restated the real question here. (I think the answer is yes but it would be good if someone could actually confirm this.)