New iMac GPU question - how do the choices size up?

Today's video cards are made to perform well in terms of 3d games and 3d modelling

A faster video card will not really help for Photoshop or video edit or word processing or general surfing or video watching

In order to help you choose, knowing the context of how you intend to use the computer is helpful otherwise we are left to shoot in the dark.

Video processing/encoding is CPU intensive. The faster the processor and

the more cores that can get thrown at it the better.

Since you don't plan to do much intense gaming or 3D modeling, pretty

much any GPU will be fine.

So, in my opinion, in your case I would spring for as much CPU as I could

afford (especially if you want to move to more video processing later). Also,

to help feed the hungry cores processing video, you may also want to consider

an SSD as well.

Bare in mind that although fast CPU's are good for video editing - all of the industry standard editing softwares out there today use GPU acceleration. So GPU is just as and in some cases more important (depending on the application and the level of GPU acceleration it's optimizes for). Final Cut for instance is VERY GPU sensitive/optimized. VRAM is very important when doing video editing. If you have the money the i7 with the M390 would be a great choice if you do MOSTLY logic and Premier just sometimes. If Premier is a major source of work for you or something you use professionally as a part of your job then it would be in your best interest to get the best GPU possible - of course with an i7 as well.