There are any number of good products available but any individual purchase could be bad with regards to the end user who purchased it. Simple statistic that applies to any product purchase.
Things are being made as cheaply as possible, with little or no QA (Quality Assurance), and usually with some rush to get something shipped.... I.e., you may receive (wrongly) a refurbished product instead of new but the shipper met the time requirements to get the box out the door.
Most products are tested under ideal conditions or with some other criteria that may be hidden in the fine print.
Scoring can be easily weighted one way or another to favor Product X over Product Y.
When I research a product, such as a PSU, I look at reviews by professional reviewers and verified buyers.
And I like to read the product(s) User Guides/Manuals, the manufacturer's website's FAQ and Forums. I look for what is said and what is not said.
There are always trade-offs: quality, availability, performance, weight, price, compatibility. ("Compatible with" makes me very cautious.)
That all said, if I find, learn, or discover that someone knowledgeable and experienced recommends or simply suggests a product it is always a good idea to pay attention. Hence the Cosair RM.
As for 650 watts - maybe.
There are online calculators to help select the necessary PSU wattage. Use two or three of them to add up the wattages of the components you plan to install. Get a consensus on what that wattage value is. Then add 25%.
Not a perfect process but it is a least something.
Your total value may end up being 650 watts as an end wattage value. Purchasing a 750 watt PSU gives you a fairly broad margin with respect to being able to add new components or upgrade to more power demanding components in the future.
May cost more to go with 750 watts. With PSU's likely a good trade-off.