However, most people believe that a slow computer is due to memory, which is a factor but upgrading to 16gigs is only going waste your money, 8GB is plenty unless you plan on running 5 virtual machines all at once, unlikely. Why, not because the machine won't accept it, because it will and if you have a good brand it will work fine and recognize it, even though Apple has clearly stated that it 8Gb is the max.
For all of your wanting to upgrade to 16BG of RAM.