My 2009 17" MacBook Pro (3.06Ghz Core 2 Duo, 8GB RAM, 512mb 9600M GT) is on its last legs. It was once the top-end MacBook Pro that money could buy ($2800), but now it can't keep up with editing 4K material from my GH4, crashes often, and just in general is showing its age. This is happening at a bad time where I've had a lot of expenses recently come up, but I can budget as much as $2100 to replace it. Video editing is the #1 priority for me, so please keep that in mind if you have any advice. I've thought about building a Hackintosh, but the more I think about it, the more I want to have a laptop. I travel a lot, and often work away from home. Really I've built a lifestyle around being able to edit on the go, and I don't want to sacrifice that. And although I am using Premiere and could theoretically switch to Windows, I have invested in other software that is Mac-only. I know that I could afford a much better Windows computer for the same price, but I'm tending to want to stay on a Mac. This leaves me just the choice between the different configurations of 2011 (non-Retina), 2012, 2013, and 2014 15" Macbook Pros. I am looking at lightly used, seller refurbished, and manufacturer refurbished options on eBay. Basically, here's what I'm wondering: How much better is the 750M (Late 2013) than the 650M graphics card? How much better are both of these than Iris Pro graphics? And how much better are all three than 2011-year Radeon 6750 graphics? How helpful is CUDA when editing in Premiere (which is only supported on the 650M and 750M)? How much of a difference does CPU clock speed make for video editing on these quad-core i7 Macbooks? How about the performance differences between Sandy Bridge (Early 2011), Ivy Bridge (Mid 2012), and Haswell (Late 2013)? I do plan on getting 16GB of RAM, since it's not user-upgradeable. I don't care as much about the hard-drive, since I plan to upgrade to a 1TB SSD a little later, once I have money to spend again and prices have hopefully gone further down. I also don't care about battery life very much. Any advice is helpful. Thank you!