I am looking to upgrade my white MacBook to a Pro because it is much too slow for editing pictures. I edit RAW images in Lightroom and CS4. Even with an external hard drive, my MacBook only has about 8GB of memory left and it runs extremely slow when using lightroom. Lightroom runs fine, but I can't use any other programs while using it or I just get the beach ball of death. What would be the best choice out of he 15" pro models? Should I save money and get the cheaper one, or go all out for the top one? I have been considering the middle model ($1849 with student discount) unless the top model is considerably better. Thanks!