It is best to install RAM modules in pairs. (2 x 4GB or 2 x 8GB)
However, if the single 8GB module is the correct specification. Then you should be fine replacing one of your factory 2GB modules and have a total of 10GB.
That is what I was thinking. The module which I was going to purchased is here. Not sure if you will be able to view it from where you are.
The are selling one 8GB module only.
Thanks for the help.
You really should get a matched 8 or 16GB kit from them.
However if your leaning towards 16GB and can't afford all 16GB now, then it will work fine to buy one 8GB module now and one 8GB later.
Apple makes the the computer and say it's best to install memory in pair...the computer comes with a pair of memory. Just follow the instructions from the maker.
However, you could certainly do as you will. To push my MacBook Pro (2008) to the edge by installing six (2 + 4) because, although it recognizes eight (4 + 4), the laptop actually becomes slower with eight...addressing issue (Apple Official max memory is 4). With the Intel processors, one can install the memory that's not a pair...works, no problem. Mine works like a champion with Mavericks and 6GB memory. For me, I just wanted to extend the life of my MacBook Pro.
Still, like stereo, memory is best installed in a pair.
All Intel Core Macs support dual channel memory access if matching modules are installed. The customary estimate is that this gives a 6% - 8% real world performance benefit.
Intel Macs are capable of gaining some benefit from using matched RAM - where both memory sticks have identical specs (not just capacity, but identical in every respect).
The benefit may be slightly more noticeable on Macs with integrated video (MacBook, Mini), where the video processor uses main system memory (rather than dedicated VRAM).