To answer my own question (kind of):
I got my hands on a X9SRA mobo. With all PCIe slots occupied (no ACS patch) the IOMMU groups are as following:
IOMMU GRoup 0 00:00.0 Host bridge [0600]: Intel Corporation Xeon E7 v2/Xeon E5 v2/Core i7 DMI2 [8086:0e00] (rev 04)
IOMMU GRoup 10 00:1b.0 Audio...