Please help me decide which 2017, 27' iMac to order. I plan to order with 16gb ram and 512 SSD, my question is if I will be ok with the lowest configuration 570 graphic card or should I upgrade that too, to the 575 or even 580. I do not do any kinds of graphics or video editing etc. just regular office work but with many browser windows, tabs, and other office work related programs open at the same time and I do not want to experience any slow or stuttering on the screen for the next 3 years. thanks for your recommendation.