if you mess around a lot with thermal paste, you really need to spend like $6 on this:
https://www.amazon.com/gp/product/B01MU2FLVJ/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
it's cheap, and it works. perhaps not the best, but for testing parts and stuff like that, you won't feel your wallet getting lighter. save the more premium stuff for final installation. actually, i've just used this for final installation and never had a problem with temps running several months straight.
I don't know anything about the case you mentioned, but all of the Supermicro X9DR"D" motherboards have staggered CPU sockets; the idea is that CPU1 hot air doesn't go straight into CPU2 heatsink. It's a nice idea in a server case, because you usually have a wall of fans pushing air threw the whole system. In desktop case, and remember when i posted this I said this is great for a NAS build, not really a workstation build, the typical fan setup is to push air over the PCI slot area, while CPUs have their own heatsink/fans. The consequence of shifting the CPU socket into the PCI area is that the onboard SAS2308 and it's heatsink are now in the CPU area. In a desktop case, this area doesn't get airflow because it mostly expects the CPU heatsink to take care of the cooling in that part of the board. You need to put some airflow in this area as the SAS2308 does get pretty hot. The other consequence of swapping the CPU socket into the PCI area is that it obstructs long PCI cards, like GPUs. The larger the heatsink you put on CPU1 socket, the greater the obstruction; so keep that in mind if you have plans to install long PCI cards.