To OP:
I believe you meant to type X5675, not X3675 in your latest post. Note that those X5675 processors work fine in the Z600 v2 workstations, and you can run either 1 or 2 of them. We run two because they are so inexpensive now, and they only need the 70W common inexpensive Z600 heatsink/fan.
I can confirm that the X5690 will NOT work on the Z600. It will work in the Z400, as an undocumented but confirmed compatible processor for that workstation. Before we started using the Z420 v2 workstations I loaded all our Z400 v2 workstations with the X5690 processor. Works great in that box.
So, don't buy a X5690 for your Z600 v2 and do buy two X5675 processors instead. Use the regular cheap heatsink/fan because that is all you need.