Different problems require different solutions. Some problems can indeed be fixed by getting the fastest CPU you can. Other problems can't be fixed by a faster CPU, because its not the CPU causing the slowness.
When you say "At the moment it takes about 6 seconds from selecting a photo before I can work on it", explain this in a lot more detail. What module are you in when you try to select it? What "work" do you want to do on it? What exactly is slow? Is this a brand new photo that has just come out of the camera, or one that has had previous work done on it?
And also tell us your current hardware and related info: CPU, GPU, disks, RAM, monitor size (in pixels), image size (in pixels or megapixels)