My 2013 vintage iMac still does everything I do with it quite well. I've not moved into making video, so even 4K is not yet a consideration. An SSD and more RAM could probably keep it happily chewing through multiple 24-50 MP photo libraries.
But, the new 10-bit, wide gamut, Retina displays attached to the new iMacs are tempting.
An 8K 30" version would be glorious...
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