I keep reading conflicting reports... Apple's website says: Memory 4GB (two 2GB) of 1333MHz DDR3 memory Configurable to 16GB for all of them. I plan on purchasing the low end 21.5" model, because not only is it all I can afford, but, it will undoubtedly be a huge upgrade for me coming from a 6 year old iMac. but... i dont know how much RAM i will be able to put into it? i was gonna buy my own RAM and install it myself. I want more than 4GB. ive read in a few threads that the low end 21.5" model wont take 16GB of RAM... then how much?