I'm still using my Mac Pro 5,1 with a (single) X5690 processor and a MVC flashed R9 290X graphics card. (I have a Sapphire RX 580 Pulse 8GB sitting on the shelve awaiting to see if Apple updates the BootROM to take a non EFI graphics card.). I recently mod'd the BootROM to accept a NVMe boot drive, and I am using Samsung 970 EVO NVMe 512GB M.2 SSD with an Angelbird Wing PCIe NVMe M.2 adapter card. The Mojave full installer has an updated MP5,1 BootROM (148.0.0.0.0) which now allows for NVMe M.2 SSD booting. My MP5,1 also has the HighPoint RocketU 1144C USB 3.0 PCIe card but I hardly use it. Thus, my MP5,1 keeps on chugging along.
That said, I really like MyHero II. If you're going to give up on a Mac Pro for audio, then the ASUS HERO series is a good to use. However, BoomR, one of our Moderators who is also an audio engineer and has recently gotten into audio/video production, uses the Gigabyte GA-Z370 AORUS Ultra Gaming motherboard based system so he can use his Thunderbolt peripherals (which the HERO X can not do). His Golden Build descriptions are a good read as is his sticky threads in the
Music forum section.
Here's his Z370 build description.