Earlier this week I received a package from OWC (Other World Computing). In the box was 4x4GB modules for my computer. I recently purchased a high-end iMac for my bedroom studio and I didn't max out on RAM because purchasing RAM from apple is WAAAAAY too expensive.
Instead I got my 16GBs from OWC...
If possible, I usually do all hardware installations myself. I've done RAM swaps too many times to count, and this installation was just as easy as others. I did realize that I have a faulty memory bank so I may have to take Whopper (my iMac) in to the genius bar soon, but it's all good!