I know 4k editing would benefit from extra system ram, so aim for 16gb if you can. How many cores/threads you'll want is determined by the software you plan to use. Because of the large amounts of data being read and written, an SSD would help. Keep in mind you can still do editing with lesser components, it'll just take far longer. You can spend money or spend time, either way it's going to cost you.
I'm just a bit puzzled why you'd buy that card for 4k work.