When it comes to chains, it really comes down to how much you want to spend. You may well want a high quality, long lasting chain but if you don't want to spend $150 -$300 for a big brand name, that's not going to happen. 520 chain price range is $40-$300. Decide what chain life you want & what budget you have, then go for it. VMX bikes generally don't need the ultra narrow chains that modern 4T bikes require either. There are some quite good non brand name chains on the market, with the same or higher tensile strength than some of the big brands, for about half their price. You just have to do a little research.
K