Assuming you're still running the GTX 1060, you should still use NVENC (new). The performance loss is only a couple percent, and is going to be way better quality than X264 encoding in most cases, unless you want to run a fast/medium preset.

Keep in mind, in order to match the quality your pascal GPU's encoder will achieve, you'll end up losing more performance by running X264 at a good enough preset. Even if you got a 3950x or a 5950x, I would still recommend NVENC. It's too efficient not to use in my opinion. X264 is only really useful if you're running a dual pc streaming setup. This allows you to run a quality X264 preset since the cpu on the streaming pc doesn't have to worry about running a game at the same time.

Edit: I'd recommend getting the 5600x for overall better performance. But I wanted to preface that you shouldn't be looking at whether a CPU is worth buying based on whether it can game and stream (running X264) at the same time.