I have observed that some aspects of SW are I/O bound, and have suggested that the relevant storage parameters be recorded in the test data, but this was not taken up so we will never know. You are not the only user apparently beaten by a Core 2 Duo.
Check out the other threads regarding computer performance and hardware - this is a good start: https://forum.solidworks.com/thread/64437?tstart=0
The main SolidWorks app is hevaily dependent on single-core speed, so a higher clock speed will equal better performance. Core 2 Duo's were clocked up to 3.5GHz, which is faster than your Xeon processor. Differences in processor architecture, and/or overclocking of the CPU could account for most of the rest of the difference.
Try reading the thread "Strange Solidworks Benchmark result" in the "More Like This" box on the right. If that is the one that I think it is, you will find that there are many very strange results posted. I would not put much faith in the site.
The very best benchmark is using your own parts, assemblies and drawings. Compare performance on your old machine and your new machine. If you have some friends with other machines, give them copies of your benchmark files and see how they do.
Thanks for the answers.
It seems that SW benchmark is quite useless for comparing other than your own computers, it uses your current settings...so for example rendering, it's quite easy to get a nice result just by using very low resolution/quality for rendering.