The Sj7 Star do alright by itself i think, i see no reason to spend more money to get a Gopro product.
The video quality is almost the same. Go Pro 5 has a stereo mic and maybe a better quality lens, but for the price SJ7 is very good, tested it's mic with my drum set (50% sensitivity), the audio quality is excellent. My one has the mic on the lens (not on the left side of the cam).