Currently I'm using 2012 Macmini with 1.5TB of Samsung SSD + 16GB RAM + i7 Quad Core in it. I'm now looking to upgrade with 2015 device. My main usage is Photo Editing and slideshows creation as a professional photographer. I've two questions for 27" iMac in terms of upgrade options 1) RAM - Is RAM upgradeable in iMac, it used to be easy upgrades in past but not sure if that is still the case with 2015 iMAc. I may go with 8GB of RAM and buy more aftermarket on my own if it is upgradeable. 2) Choice between 512GB SSD v/s 2TB Fusion Drive. Which one give better performance. Normally I like to keep project I'm working on in my internal drive. Once completed with the work I upload everything to Amazon Drive online as well as to External Backup drive. Normal Wedding shoots yields anywhere from 60-90GB of data so having internal space available is good. Any advise ?