CPU-Z Benchmarks on various Synology models - Hope this helps give a rough idea of the CPU power difference between models. Also included 2 other VMs running on Windows Hyper-V Server. :
The new Cycles CPU 2.79 Benchmark - Blender and CG Discussions - Blender Artists Community
Xeon - Wikipedia
Intel Xeon X5670 Dual 6 Core Processor Benchmarks and Review