I have a 27-inch Mid-2011 iMac, 3.4 GHz i7 with 24 GB RAM, and a 5TB external drive with my iTunes Library on it. I have Home Sharing on, and stream to four AppleTV's, and sometimes a laptop or two, throughout the house. I am streaming Movies and TV Shows, mostly in Playlists that last all day, to the AppleTV's. I do very little photo editing on the iMac, because the majority of it is done on my 13-inch Retina Early 2013 MBP, which handles it much better, and is my day-to-day machine. The iMac is having some problems, mostly with the AppleTV's not being able to find the Library. I either have to restart iTunes or restart the iMac to get it to work correctly again. What specs should I be looking at to replace the iMac? Since it is mainly used as a media server, I don't know if I really need a high-end iMac, but I do want something that will last a good 5-7 years. I also may switch to it for my photo editing at some point, as I feel constrained with the 13-inch MBP. I hesitate to get the 21-inch, as the RAM can't be upgraded. My other option is to use my current MBP as the media server, and get a new 15-inch MBP for my photo editing. Any advice?