I'm debating between an Early and Late 2013 15" rMBP. I can get either one for around $1600 (open box late 2013, refurbished early 2013), which is my max budget. 8gb is enough for me, but with the Late 2013 (or Early 2013 on iGPU), I know the iGPU uses a portion of that (up to 1gb for the Iris Pro and 512mb for the HD4000, I believe?). My question is this: In those instances, if I force it to run on the dGPU, will that free up all the memory used by the iGPU, or does it still borrow some? Also, does anyone have any experience with the thermal impact in forcing the dGPU to operate in a non-graphic intensive situation (say, compiling something or editing audio)? The majority of my system intensive work (software development, audio\video editing, graphic design, or games) are done where I can plug in, so the battery impact of doing this isn't a big deal, but if the GT650m just naturally roasts the system in even light use, it would worry me.