I upgraded my 2009 4.1 to 5.1 with a new X5677 CPU. That went fine. Upgraded to a GTX680 flashed, and that made some operations quicker, though the Geekbench scores stayed the same. So next step was Sierra over El Capitan and I installed that. Most software works so far. I lost Paintbrush but installed Eazydraw instead. The most significant thing so far is I've lost WiFi. Not an issue at present since I'm using a cable to my router. Am I right in thinking I need to swap my WiFi card for a BCM94322MC? Looks fiddly but do-able. Any other common issues on the horizon?