Chosen Solution

I own a late 2014 iMac 27” retina display with the Apple’s 256 GB SSD. What is my best storage upgrade option, assuming by “best” I mean fastest (I’d settle for a 512/ 1 TB SSD option). -edit- I’ve found this combo: NGFF M.2 nVME SSD Adapter Card + WD Black SN750 NVMe - apparently the adapter fits into the iMac (although it might be tough to install the adapter), can anyone confirm that this would work on my computer? Thanks!

If Speed is your issue then surprisingly an external drive will be faster! The cheapest solution would be a OWC ThunderBay 4 That can get you 980 MB/s of sustained throughput!