I want to upgrade the CPU/Processor (is that the same thing?) from the current Intel Dual Core 2.0 to an i5 CPU. The PC is a small form factor Dell Optiplex 745 model, very thin. I watched a video of how to upgrade that specific model's CPU so I think I can do it but I want to know how high I can upgrade it. Even an i3 CPU would be better than my current one. Many thanks in advance!