I have a P3P. I am using Windows 10 64-bit with 32GBs of RAM and an ASUS A88X-Pro mobo.
My APU is an AMD A10-7850K.  

Problem is stuttering when trying to view/edit 4K videos. Might this be that I am using the APU as my 'graphics card'? If so, what is a decent card to install, and being under $500 or so?

I use both a desktop and laptop for editing.
i-7 3770k nivida 980
i-7 5700m nivida 965m x2

If your lucky you can pick up a gtx 980 for close to your budget. I would only bother doing this if i also played a lot of games. I know that the i-7 are considered some of the best when it comes to video editing. Someone will correct me if i'm wrong, but i always understood the cpu was the most inportant part in video editing.

Don't buy a 980 the 1080 is being released.

The price for the 1080 is going to be right around 600.00usd, and to tell you the truth, they are both overpowered if all your doing is video editing.  Gaming is what drives this market for these cards.

DaddyOhh Posted at 2016-5-31 17:36
I use both a desktop and laptop for editing.
i-7 3770k nivida 980
i-7 5700m nivida 965m x2

True CPU and memory is the more important for editing. The Graphic card for rendering work.

As has already been said, the CPU is the most important item, i use an i7 6 core CPU with 32 GB of fast RAM and an older Nvidia GPU card. What video card you choose depends upon which one is supported by the editing program you have, not all video editing applications support every type of GPU card. A supported GPU will give you good preview capability and speed up the render process. The best editing package by far is Blackmagic Resolve, and the light version is free. But it does have a requirement for GPU support. You can check it out here: https://www.blackmagicdesign.com/products/davinciresolve