The absolutely best PSU would be the XPG Core Reactor in that price bracket. Comes with a 10 year warranty as well.
Though it's mostly out of stock online. Why of you ask me, I had a talk with an online retailer and he told me that under modular category of power supplies in India, people mostly prefer 750/850Watt ones so 650W ones are either less in stock or due to less demand retailers don't restock them.
also, did you end up buying that NZXT PSU for 6k when it was going on in an offer?
All in all, go for atleast a B tier PSU. If the budget is a constraint then you can leave the Gold rated ones and go for a bronze one. One such B Tier Bronze PSU is Asus Tuf 650B. It comes with a 6 year warranty.