What monitors are compatible with a 2017 iMac?

youradviceplease wrote:

Dell 34 Curved USB-C Monitor- S3423DWC (£439)

Dell – Dell 34 Curved USB-C Monitor – S3423DWC

That's a 34" ultra-wide monitor with 3440x1440 resolution. It has a USB-C input, two HDMI inputs, and built-in speakers, but no built-in Webcam. The pixel density is about the same as a standard 27" 2560x1440 monitor – the extra pixels go to making it wider, not to providing any sort of Retina-like PPI.

Panel technology is VA (not IPS), but the viewing angle (178 degrees) is good (as with IPS), and sRGB coverage (99%) is also good. So color accuracy should be decent.

BenQ PD342OQ Designer Monitor ( AQCOLOR Technology, 34”, 21.9 Ultrawide, WQHD 1440P, P3 Wide Color, USB-C

£648 ( getting to be v expensive)

BenQ – PD3420Q｜34" WQHD BenQ Designer Monitor

This one is another 34", 3440x1440 pixel monitor. So it would display the same amount of stuff, at the same size, also without any sort of Retina-like PPI.

This one has an IPS panel, 100% coverage of sRGB, and 98% coverage of the wide gamut DCI-P3. Coverage of a wide gamut (Adobe RGB and/or DCI-P3) is something that professional photographers often look for. (It can help with making sure that colors on printouts closely match those on the screen, if you are willing to put in some extra effort to use a color-managed workflow.). It also has 10-bit-per-channel color (1.07 billion colors), compared with the 8-bit-per-channel color (16.7 million colors) of the Dell monitor. This means that within a given color gamut, it can offer finer steps between different shades of colors.

This may be in software, but it apparently has some feature to make it easier between working with different types of color profiles (different color gamuts?). Something that would go along with it being designed for the needs of professional photographers who want extra color accuracy features and are willing to live with their complexity.

The good DCI-P3 coverage might also make this monitor a little better than the Dell one for playing Digital Copies of Hollywood movies. DCI-P3 is a standard that comes from the movie industry and Ultra HD TV worlds.

So I see why people would pay more for this monitor … but at the same time, it sounds like the features that make it more expensive are not necessarily ones that you need. BenQ surely would not mind if you bought it, but you're not the target market.

Dell SE2722HX 27 inch Full HD (1920x1080) Monitor, 75Hz, VA, 4ms, AMD FreeSync, HDMI, VGA,

£114.99

a little smaller than I ideally want as I want to see my clients easily as we all do the exercises.

That monitor is very large relative to its resolution. If you put it on your desk, and use it for Web browsing, word processing, etc., there is a good chance that you will find the text to be uncomfortably large. (Assuming you've got normal eyesight.). 1920x1080 resolution isn't high enough to allow any fix other than pushing the screen far away from you.