I think the thing is that anyone that has this kind of often rare and expensive hardware probably isn't that interested in Nebula, and most people...
I've been running an Arturia 8-Pre as an ADAT expander with an RME AIO and it's solid. Great pre-amps in it too.
I haven't really tried the IK Mixbox, but I do like the Slate VMR if only for the analog summing module which I think sounds pretty good.
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