Andrew,
I need two PCI slots.
I'll try luck with SuperMicro X9SRH-7F ( holds up to 12 cores and up to 135W).
It has 3 PCI,
It has more than any consumer X79 MOBO can offer:
-SuperMicro claims that Intel C602J chipset version, implemented in X9SRH-7F is a long-life version of C602: 7-years of 24-hours service (Intel positions the C602J for "Mission critical applications").
-It supports registered, ECC memory with errors correction.
-It has LSI SAS2 controller on-board - to use SAS HDD instead of SATA as a storage option. I assume this may contribute to sound quality. You even can use dedicated integrated controllers (Intel & LSI) for a OS drive & a media HDD, respectively! LSI controller uses direct to CPU PCIe x8 lane independent from PCI.
(good reading on SATA v.s. SAS topic
http://www.enterprisestorageforum.com/s ... ata-1.html).
-MOBO's BIOS settings allows to take specific amounts of RAM from OS & allocate it to hungry PCI devices, & have such exotic feature as 5% CPU clocks de-synchronization which aims to reduce EMI.
-It has Matrox 200 (16Mb DDR2) - graphics on-board, capable to hold 1900 x 1200 res. after driver tweak

However, I have to admit, that integrated video in this MOBO is, actually, no use, as it resides on the PCI bus & heavily loads DMA. When integarated graphics is in use, Pyramix in MassCore mode will report "DMA overload" (up to 65-70% idle) & a "poor PCI response time".
- Last, but not least, it has IPMI with KVM, which allows you totally manage your DAW server distantly (resides on the same PCI bus thou)!
There is a cheaper option: SuperMicro X9SRA MOBO, but it has only 1 PCI slot, no VGA on-board (not sure about IPMI), no SAS controller, and standard, not a long-life version of C602 chipset.
After all, when I look on my SuperMicro server MOBO & compare it with my modern consumer mobos like ASUS Z97-A or Gigabyte Z97X-UD3H (not cheap, thou), I have to observe, that the SuperMicro bears twice as many crystal oscillators as the latter. I'm not about to assert anything, I'll better stick to a PRO hardware solution instead.
PS: Now I can confirm: I've installed Mykerinos PCI card into the SuperMicro X9SRH-7F MOBO on Xeon E5-2650 CPU (characteristics are identical to modern E5-2640 V2, namely 8 cores 2Ghz, 20Mb L3 cache, 95W TDP), with an offboard graphics (AMD 2270 - passive cooling, only 10W TDP) Windows 7 x86, Pyramix 7.2, MassCore, 4Cores for Windows + 4 Cores Dedicated, works fine (without Hyper-threading)! DMA idle load within 25%. DMA 31% (6ch 24-192kHz output monitoring). ASIO works with Jriver19, however mixer is not available. Beware of the LGA2011 narrow ILM type - choose appropriate CPU cooler (for example, Noctua NH-U12DX i4).