It has very little to with the graphics card, the only thing it can do while editing, is act as an extra processor, by using OpenCL. (...) Maxing out graphics will get you nowhere. The M380 will do fine.
I beg to differ. A GPU is very important for video editing as it is for for games.
There are a lot of moving pixels, which demand very complex renderings and transcoding.
And as you mentioned, GPUs can also act as CPU, offloading some heavy lifting from the main processor.
That's why the professionals (there are several threads going on about the upcoming Mac Pro) are demanding nVidia GPUs, not only with large amount of memory, but also high number of cores, which have the CUDA technology, supported by the majority of video applications (from video editing, to visual effects).
The most important thing is the Intel i7 processor.
Indeed. The brain is the brain and there's nothing you can do without a good one.
Having 16 GB RAM might not be a bad idea either.
I would start with 16 GB. It'll be very useful and not as much as one might think.
Also, It means 2 x 8GB modules, instead of the 2 x 4 GB of the default configuration.
Since you can access the RAM, you can, if needed, upgrade your memory to 32 GB.
All these things will make your system last longer.
In the end, as I said, it all depends on what you want to do and what it demands.
