I was down to look at two imac's 27". I couldn't see them side by side unfortantely, but I got a good look at both machines. The 5k seemed a little laggy, when moving windows around. I am not sure which graphics processor it had, but I am pretty sure it was the base model. After looking at the 5k model, I could easily see the difference. The screen is nothing less than stunning. It reminded me of the first time I saw an LED TV. Anyway, I am in the process of buying a MAC. I have never owned an Apple product before, so this will be my first I have 3 configurations in mind: The non-retina iMac: 3.5 i7 8 GB 256 GB SSD GTX 780M 4GB The Retina iMac with i5 and M290X (+$300): 3.5 i5 8 GB 256 GB SSD M290X 2GB Or the maxed out Retina iMac (+$600): 4.00 i7 8 GB 256 GB SSD M295X 4GB For all 3 machines, I will add more RAM later. The price difference isn't really that big and when we're talking about these kind of numbers, it doesn't really that much. I am a little concerned about the AMD GPU's. I really don't want to spend $3.000+ on a computer and then have to be annoyed about lagging or noise (which seems to be a problem with the 5K machines). What should I do?