I recently did an upgrade and went with a Intel dual CPU solution and am very happy with it. My build is detailed in this thread here
The 8 core CPUs I went with were 290 each and the 10 core chips I wanted we're 500 each and I bought used ones. I think you'd be able to get 12 or 14 core chips for about 5 or 6 hundred each but at a lower clock speed like 2.5 to 2.8. My chips run at 3.2. My motherboard is awesome but it doesn't have IPMI. IOMMU grouping is fine and the onboard LSI HBA flashed to IT easily. Let me know if you have questions and I'll help where I can. Oh, I run 4 GPUs in it now.