I ordered the 27" 2012 iMac and for sure want to upgrade my own RAM, my own way. I have a few sticks from my workplace, which is 2 x 4GB at 1333 Mhz. Simple questions here: 1. Should I just keep my sticks and plug them into the iMac? Or should i take the extra effort to upgrade my RAM to 1600Mhz (4 x 4GB) is enough for me so I wouldn't take the 8GB sticks. 2. Is there any real world difference between those clocks? GPU has its own GDDR so that's not a problem, right? Don't tell me to go with the 1600 because it's so cheap. I have1333 with me already. So should I keep them or be worried and upgrade? Thank you.