Dual FirePro cards, mini PCI-E SSD, and up to a 12-core [single] CPU? I feel like this will start north of $3500, but they might have a cheaper base config. Maxed, it'll probably top $5k.

Sounds about right. It's nice to imagine them doing a version with a single socket and a nice-but-consumer-level GPU -- that would finally be a worthy embodiment of the mythical "xMac" -- but they've been actively disinterested in releasing a headless mid-range machine for years, and I can't see that changing now.

"a worthy embodiment of the mythical "xMac""

It would certainly look great next to whatever black non-apple monitor(s) or TV(s) you wanted to plug into it.

Looks like this version is single socket only.