I have a single quad core 2.66 MP 4.1. Wondering where to go from here: 1. Upgrade CPU to W5590 and not bother flashing to 5.1. Easy option, some speed gain. 2. Upgrade CPU to X5677 or W3680/X5680 and hope the 5.1 flash goes OK and I don't get problems 3. Get out of Mac Pros altogether and use a Mac Mini. I already have a 2012 Mac Mini second computer. Is it worth hanging on with El Capitan, when Sierra poses more upgrade problems even with the 5.1 flash? Or is it only a matter of time before the next OS ditches the Mac Pro 5.1 and the whole thing just isn't worth it?