Researching to replace my 27" iMac with a 24"

[iMas70]

Have you considered rebuilding the 2015 iMac? If it is no longer used, and you are willing to sell it. I would rebuild it as a display only.
That's what I did when my late 2015 27" died. And others are also happy with their new DIY 5k Displays.

https://forums.macrumors.com/threads/diy-5k-monitor-success.2253100/page-102

I’ve never thought about that but it may be something to consider. I’ve mainly considered buying a new computer then selling the two 27” to offset the cost.

 

[StoneJack]

My advice
1. Your iMac 27 is very fine for computing and you dont need to upgrade
2, consider buying a used m2 air if you really need m chips and use in combo with imac
3. Macmini of any m and Dell 27 2k combo will replace ur2017 imac