I'm not sure about 384 GB
If 384 GB was really needed for virtualization on a two processor system, you have to ask why Cisco didn't use the VMmark benchmark results they published to prove the point. But funnily enough they used the same amount of memory as just about everybody else (96 GB in the form of 12x8GB DIMMs). To me this suggests that memory beyond 96GB for a dual processor is probably a waste unless you have workloads that have a very large memory footprint relative to CPU and I/O requirements.