Hello, I have to choose a workstation that I will be stuck with for the next five years (institute policy). Could anybody knowledgeable please compare these processors? I will be running windows on the workstation. For the HP-Z820, I cannot buy a system with one E5-2687W, I need to get two processors. E5645: 6-core on the MacPro W3680: 6-core, 3.3GHz on the MacPro W3565: 4-core, 3.2GHz on MacPro E5-2643: 4-core, 3.3GHz, 10MB cache BUT 3.5GHz under turbo boost!? E5-2690: 8-core, 2.9GHz, 20MB cache (somewhere I read that with turbo boost, it can run at 3.8GHz which is the same as the E5-2687W.) E5-2687w: 8-core, 3.1GHz, 20MB cache (3.8GHz at turbo boost) Thanks.