Memory upgrade options for iMac Pro? I'm considering getting an iMac Pro. I'd love to max out the crazy amount of memory but beyond my budget. Thinking of getting 64 GB RAM. If I did want to upgrade after purchasing, would I need to get 3 more 64 GB units to fill it out or does it not work like that for this machine?

Note: I do understand that upgrading is not easy and I would take it to a certified place to get it upgraded - just hoping to save some $$$ this way.
If you get the 64 GB option, then this would be four 16 GB units. Basically, Apple is going to ship the computer with the four memory slots balanced with the same memory size. So when you upgrade later, some (if not all) of the memory you paid extra for will be replaced.