Dell has something like thirty 27" monitor models on their site, but when you add the filter "4K", that drops the list down to six, of which only two are in your price range. Those two appear to have IPS panels and 99% coverage of sRGB (narrow gamut), but no specified coverage of DCI-P3 or of Adobe RGB (wide gamut).
BenQ originally made their name with inexpensive photographers' monitors (around $600 for one which featured hardware calibration and a hood, if memory serves), but it looks like success has caused them to "go upscale".
On the ASUS site, there are the
The 279CRV has an IPS panel and 99% coverage of the DCI-P3 and Adobe RGB wide gamuts. The 279CV (no "R" in the name) has 100% coverage of narrow gamut (sRGB), but is not advertised as having good coverage of either wide gamut. I no longer see prices listed on the ASUS site, but both seem to go for $400 at places like B&H Photo Video and Amazon. I don't think either has a built-in microphone, so if you went with one, you might need to get a separate USB microphone.
The USB conference microphone that I use has silver trim, and a glowing red/green circle on top to tell you whether the microphone is enabled. It lives on a monitor stand, but if I put it on top of a modern Mac mini, it would look as if a UFO that was roughly the size of the Mini had landed, and was seeking to make off with the Mini …