PC830 is the only one in the range without hardening, therefore it's worth buying the 850. Above that they are all the same functionally, although the pricier ones look nicer.What are the quality 8 speed chain options? My son is going through PC830 chains in under 600 miles and that’s road riding! He does oil them and keep them reasonably clean.
There are so many counterfeit chains around that I only buy through decent retailers now.