I have 3 Mac Pro 3.46 12 core.
All of the systems are HDX 3's
All three of those are running High Sierra .
I purchased 3 NVIDIA Quadro K5000 4 Gig Video cards.
for them. They are the best cards to use with my HDX cards
because they only use 1 power cable.
All the above systems 64 gigs of ram each.
They are full of SSD's along with a 10 TB rotational drive
for back up in each machine.
I have another 2.66 12 core for Video that uses a Native card .
It has a stock 5770 video card, 64 gigs of ram and an Aja Kona
4 card for video being projected.
We do Immersive Mixing... Dolby Atmos Theatrical and Home Theater,
DTS X and IMAX. These systems are rock solid and are up to the task.
I will update to Mohave as soon as the project I am on is finished.
I purchased my Video cards from Gary of GSharp Music
http://www.ebaystores.com/GSharpMusic
He's the best!!