Need help deciding on a video card for cMP

[DEMinSoCAL]

I had a GTX 960 2GB card in my cMP (4,1->5,1), but moved it to a different "souped up" cMP that I setup for a relative that wanted a cMP for work.

So, now I'm rocking a Apple 5570 1GB in the mean time , and having just acquired a couple Dell P2715q 4K displays, I'm wondering what to put in my system now.

I don't game, and I don't anticipate doing any professional video editing. Just general apps, Adobe CC, etc.

I need something to drive the dual 4K displays (via DP). I think I need 4GB cards, but I can't decide between nVidia and AMD. I think the 960 isn't powerful enough (or is it?) so looking at a 4GB GTX 970. On the AMD side, looking at a 4GB R9 280X (or can I get by with a 4GB R9 270X?).

nVidia = low power but no boot screens and always chasing web driver updates.
AMD = if I get a flashed card (more $$$), I have boot screens, but cards use much more power and run hotter.

I want to keep the cost low, but I want the best bang for the buck to drive these two displays.

What would you suggest?

Thanks.

 

[ActionableMango]

I don't know much about 4K, but I believe all of the choices you picked support it.

The GTX 970 can be flashed for boot screens too.

 

[DEMinSoCAL]

I don't know much about 4K, but I believe all of the choices you picked support it.

The GTX 970 can be flashed for boot screens too.

I knew they supported it, I just was undecided which property of each card was more than the other...one card faster than the other and if so, I would have to decide of power consumption or no boot screen was a bigger issue.

Nice to know about flashing a 970, though. I'll have to research it.

Thanks.