I have a mid-2011 iMac. It has a 2.5 GHz Intel Core i5. It’s starting to show it’s age, especially when it comes to photo editing in Lightroom. I’m thinking about a new iMac (also open to PC) but I don’t fully understand processors. Photo editing is probably the most intensive thing I do on the computer and don’t do it very often. What should I be looking for in terms of specs on a new iMac?