The performance of the units is not up to the processors only. I can give you this link so you can compare the processors side by side and check them.
http://ark.intel.com/compare/37096,47920
Based on that information I can tell you that the X5670 processor is much better that the E5506 processor.
My recommendation in this case is that you contact the manufacturer of the server or if you want to use an Intel server motherboard contact the Intel Servers Support Team and the can provide you specific information about the server you need.
