I would agree the Enermax is slightly better. I've only trusted my workstations and servers with Enermax.
I have not overclocked this particular Xeon yet, but on forums, I know that this Xeon will overclock to 3.87GHz with the gigabyte board that it is on. My limitation is the memory. The ECC on the server-type ram is the limiting factor; and I never bothered testing it. I built it for stability more than overclockability. I do not remember this sytem every hanging or freezing. Ever.
By the way, this system will come with licensed Windows 7 Enterprise 64-bit (w/SP1). That is the corporate equivalent for the (retail) Ultimate.