Hello. Long time lurker, first time poster. Been waiting for a long time for new iMacs to come out to replace my 2009 Mac Pro. I've read on a few posts, but nothing in detail, that the new 27" Retina iMacs support 64GB of RAM even though the Apple store only allows you to upgrade to 32GB. So is this true? If I were to purchase a model with the base amount of RAM, could I buy 64GB of RAM from a 3rd party? OWC, Crucial? If so, who would you recommend and would that type of RAM be available anytime soon? Thanks in advance!