researching the iMac 27" Retina Display . . . . . . . . . your thoughts and insights are welcome

I have 24gb in my iMac, 2 4gb and 2 8gb (from OWC). Works fine.

Not much, I doubt that I would ever really hit a wall with 8gb. But I really just want a computer capable of taking whatever I throw at it. So it sounds like 24gb should be enough.

I have 8Gb in my Mac Air, but I would gladly take 16+ if available.
Better to not need and have than to need and regret.

If it were me, for 'future proofing' I would pony up the extra cash for 32gigs and be done with it.
You could sell the stock 8gigs on eBay or perhaps to another user on this thread. To allow them 16gig via 4 slots.

RMyers wrote in post #17777582
I have 24gb in my iMac, 2 4gb and 2 8gb (from OWC). Works fine.

I think this is what I am going to do. Basically for 32gb I would have to replace my current sticks, meaning it is "wasting money" (I would not sell the OEM sticks in case I need to send the computer in). 24gb is the most cost effective, and I doubt that I would even use my full 8gb anyways.

One question, do you use the two 8gb sticks in slots 3 and 4? Should I take the OEM sticks out of the first two slots, and then put those in 3 and 4? Or does it not matter which order the sticks are in?

Myboostedgst wrote in post #17781026
I think this is what I am going to do. Basically for 32gb I would have to replace my current sticks, meaning it is "wasting money" (I would not sell the OEM sticks in case I need to send the computer in). 24gb is the most cost effective, and I doubt that I would even use my full 8gb anyways.

One question, do you use the two 8gb sticks in slots 3 and 4? Should I take the OEM sticks out of the first two slots, and then put those in 3 and 4? Or does it not matter which order the sticks are in?

Mine just went into slots 3 and 4. I later had a hardware issue and swapped them around to diagnose potential memory issues. Worked fine that way too. FYI, Apple replace main board and power supply to fix problem. It would crash when hot (after 2.5 years of no issues). Applecare paid for itself on that one.

We have a 2015 IMac retina here, it's a nice machine. No issues with it. I'm a bit cautious of the late 2015 IMacs - the ones recently announced with Skylake processors - Apple changed the color gamut of the displays to DCI-P3, greens and reds are different. Photoshop CC 2015 has a DCI-P3 setting, the old CS6 does not.

OS X El Capitan: Set your display’s color profile

https://support.apple.​com …locale=en_US&lo​cale=en_US