Read through this post. https://forum.solidworks.com/thread/64437?start=0&tstart=0
Highest clockspeed with the most modern Intel cpu architecture is what you are looking for. Core SolidWorks is single threaded for the most part.
I would be tempted not buy that machine you have listed. Dual cpu's at a lower clock speed are not the way to go. Get a newer cpu, higher clock speed, quad core. Properly spec'ed an up to date, single socket, quad core cpu will run circles around the 4 year old Xeon X5620's. Will not break the bank as well.
Be sure to get an approved graphics card. http://www.solidworks.com/sw/support/videocardtesting.html