I have the base 27 inch 5k 2015 model with 1 TB spinning HD. Here is the speeds right out the box booting from internal 1 TB spinning HD. After using CCC and here are the speeds booting from an externally attached USB 3.0 1 TB SSD. I did not choose thunderbolt due to the cost and marginal benefits after research. Case: http://www.amazon.com/gp/product/B00FCLG65U?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00 SSD: http://www.amazon.com/Mushkin-MKNSSDRE1TB-Reactor-SATA-2-5inch/dp/B00PAFJJRA Although not the apple speeds of 1k + read/write. It's great for most people's needs. This is one for my parents so they are using it for more day to day browsing. This also doesn't void warranty and allows for easier resale.