Get the new iMac 5K at B&H Photo and see the Lloyd’s computer gear wishlist. Save money on 32GB or 64GB OWC memory (about $400 savings vs Apple!). MPG recommends this iMac 5K: 27" Retina 5K Display, 4.0 GHz Intel Core i7 (Skylake), 1TB Flash, 8GB memory, AMD Radeon R9 M395X GPU (4GB GDDR5) + 32GB or 64GB OWC memory.
The iMac 5K has a display with 14.7 million pixels (5120 X 2880). That means that a 12-megapixel Sony A7S II image (4240 X 2832) won’t even fill the screen, though it comes close vertically.
Food for thought: the Sony A7S II or any camera with less then 50 megapixels won’t even fill the computer screen you’re likely to have in 2-3 years: an 8K display.
Apple has 5K (5120 X 2880) as of 13 months ago. How long before Apple has an iMac 6K or 8K? An iMac 6K would require a 24-megapixel image, and 8K would make even the Nikon D810 inadequate to fill the screen.