The requirement is:
I need to be able to replace my MOTU 3 x 24I/O system with an equivalent MOTU AVB one (I blame the new converters and nothing else for this). CueMix currently allows me to monitor all my hardware MIDI gear (over 60 inputs) for near-zero latency overdubbing and MIDI tracking. It also allows me to bring drums, bass and the rest of the input signals into my little Mackie Onyx on 3 discreet (mono and stereo) channels, thus providing a convenient means by which I can quickly balance the most useful (aforementioned) categories for said overdubbing. Crank the drums and bass for bass tracking, the drums for drums and so on.
The questions are:
1) Is the AVB system capable of providing all these inputs (plus guitar, bass, vox etc.) to me for monitoring the way CueMix does? It appears from the literature I’ve seen that each unit sports a 48ch mixer, but as I mentioned, I need upwards of 60 channels to be routed to the Mackie in several groups (along with DP’s main outs, of course, also to a discreet pair which occupies a stereo channel on the Mackie). I don’t care about all the fancy effects on offer; volume and pan per input will suffice.
2) Is it even possible to run this system on my 2012 Mac Pro? I saved for 6 years and upgraded to the last desktop (non-trash can model), buying in at 2.4GHz with a view to a future CPU boost. HCMarkus’ efforts to keep us up to date in this regard have helped this all come to a head for me now as I try to balance waiting for an announcement from Apple (on where it’s going with the Mac Pro range) with keeping and upgrading my Mac Pro (before the X5680s run out/become expensive on the s/hand market), and of course the MOTU AVB upgrade.
3) If not, is there a way to add thunderbolt to it?
4) If TB simply cannot be accommodated on this machine, would an AVB-capable ethernet card allow the performance I require?
There you go. This stuff has been the subject of many a nightmare (and daystallion) over a period of many months. I’ve desperately wanted to rejoin my Unicorn buddies and ask y’all what my options are, but as many of you are probably aware, confidence, energy and indeed health have been at a premium orders of magnitude beyond that which I’ve been able to afford. As I said, it’s all come to a head and I feel compelled to consult the most eminently intelligent, kind, understanding, honest and reliable folks I know, so it’s off to BeeGutz and I’ll catch y’all ‘round the traps.

NOT!
Thank you all so very much from the bottom, middle and upper regions of my heart. Heck, I’m already grateful and you haven’t even uttered a neigh yet.
Ready… set… NEIGH!!!