My current Mac Mini (late 2012 model) works just fine. Recently upgraded it to 8 GB RAM. My needs are basic. Using an Apple Cinema Display 20". This is a beautiful S-IPS panel. Got it in late 2009 when discontinued and it still works just fine. So in reality I'm in no need to upgrade my desktop. However at some point I will need to and I'm intrigued by the 21" 4K iMac. I don't need anything larger than a 21" screen. I went to my local Apple store and gave this model a close look. Yes the screen looks sharper than my current setup, but I can't say it was all that noticeable. Perhaps I'd feel differently looking side by side. Also my current screen is matte and my home office has a ton of ambient light via a variety of windows behind my chair. I am a bit concerned about the glossy screen of the iMac. (I know the 2017 models have more anti-glare but still.) Anyways, I'd love to hear from others if they think the 4K iMac would be a noticeable upgrade given what I have. Also I could get a 4K monitor plus a new Mac Mini down the road (maybe a redesign this year?) as the one I currently have can't support a 4K monitor.