I have a 2011 iMac with 2x 2GB of ram that it came with from apple. I just bought 2x 4GB from crucial. Can i just insert those 2x 4GB in the empty slots or do they have to go in the first 2 slots? Which would mean i have to swap the 2x 2GB down to the bottom and put the new ones on top. I always thought the larger ram needs to go in the first slot and let the smaller ram follow it in descending order.