Upgrading RAM questions

No. There is a slight performance improvement from using matched pairs, but you could have 2 matched pairs that do not match each other.

MR Guide to Matched RAM on Intel Macs

Link to where you read that?

 

I would get the 2x4 GB upgrade to bring your mac to 12 GB total. That seems to going in the $40 range.

Then, in the future if you want more ram, you can buy another 2x4 GB upgrade to bring you to 16 (by replacing the 2 GB sticks).

Ram should be installed in pairs for best performance.

When you put the new ram in your iMac, you can just put the new ram in the free slots.

 

Here's what Apple says about the positioning of the new RAM in the iMac:

-If you install additional memory modules, insert then in the open slots

-If you replace the installed memory modules, insert a new memory module in each of the slots furthest from the display

 

I'd say he is most likely referring to Quad Channel Memory:

http://en.wikipedia.org/wiki/Multi-channel_memory_architecture

Scroll down close to the bottom of the article. IIRC benchmarks I've seen give something like only a 1-3% improvement on average. I've moved 2 x 2GB over to my Mac from my MacBook Pro (same memory as what is installed in my iMac) and I've noticed no performance increase over and above what one would expect from a memory upgrade.