1st. CoolerMaster doesn't manufacture server cases.
2nd. If you mean any CoolerMaster case that will fit server motherboards then:
The 6-core AMD Server processors are different than 8/12 Core processors.
6-core are Socket F Opteron.
The 8/12-core are Socket G34 Opteron Magny-Cour Processors.
It really depends on the motherboard though. If you get a single-socket, they're generally ATX, and then most cases will fit them.
Dual socket can either be SSI CEB, SSI EEB, or E-ATX. E-ATX is generally the most prevalent in motherboard support. CoolerMaster ATCS 840 is a case that fits E-ATX.
SSI form factors are harder to find support. One of them is compatible with EATX. The other is not. I don't remember which one is which. You're better off looking to actual server chassis manufacturers for SSI EEB/CEB form-factor support.