I've seen some benchmarks and the 8400 looks to be about as good as a 7700k. Would the 8400 pair with a 1070 nicely for a few years? Or would my brother be better off going for the 8600k? He's on a relatively tight budget so the saving would be helpful if there's not much to be gained in going for the 8600k. I can find the link which compares the 8400 to the 7700k amongst others if anyone is interested.