You are looking for a workstation class motherboard. They can support up to 4 CPUs of the same socket type. The CPUs should also be of the same type like 4 Intel Xeon E5-4600. These types of motherboards tends to be expense ($2,000+) because they are meant for large enterprises.
If you want combine several non server CPUs together, especially of different models / generations, then it will be a bit more complex and expensive since you will need to custom design a motherboard, chipset, and software to do that type of feat.