It should mix properly in this configuration in the next build. It still feels a bit awkward to have the empty channels positioned where they are, but its just legacy now.
Agreed. It's a bit of a compromise. I'm used to doing this sort of routing in hardware but I picked up this Topping Dm7, and it doesn't support any kind of routing / channel assignment internally.
It's essentially the only affordable, acceptable quality 8ch D/A on the market that you can actually get in your hands, it's competitors are the Okto which you can't buy now, or the ExaSound units which are significantly more expensive.
I'm actually blown away by the Dm7, got it hooked up yesterday and I've been in awe. I hate to be one of those blabbering audiophiles going on about how changing a piece of gear 'brought tears to my eyes' but the way it renders some passages is just absurdly beautiful, there's almost this 'effortlessness' where even quite hot, or harsh mixes still render without any added distortion in the HF, a place I found some decently high end audio interfaces struggling with. It's really quite clinical and neutral which is exactly what I'm after. I'm not here to have crappy recordings or mixes sound good, I just don't want them to sound any worse than they have to.