More Expensive PSU has better Quality Higher amperage?
Maybe - maybe not.
Best way to tell is to find an independent review of the PSU (like that Jonny Guru site). That way, you know you're buying a good PSU.
The Green Power site is saying it's PSUs work at 80Plus efficiency.
--> But I can't find any of their PSUs listed on the 80Plus.org website
. That should be a warning indicator.
You should find a good review of a Green PSU (from a review site you trust) before you trust them with your money.