fazlollah :
i thought he was going for a budget build !!!!!
u never regret if u go for a high quality PSU, but in this case i think even bronze/silver series are enough.
Seasonic S12II series PSU is the cheapest PSU series Seasonic offers while still having good build quality. Same can be said about Seasonic G series that also is priced fairly cheap while offering better efficiency and cabling over S12II series.
For a premium PSU, look towards Seasonic Platinum or PRIME series.
You can't rate PSU by it's efficiency alone. For example:
Aerocool Strike-X 1100w,
specs:
http://www.aerocool.com.tw/au/psu/strike-x/strike-x-1100m
vs Seasonic S12II-520,
specs: https://seasonic.com/product/s12ii-520/
Aerocool Strike-X 1100w PSU is rated 80+ Gold while Seasonic S12II-520 is rated 80+ Bronze. When taking into consideration that higher efficiency = better PSU then Aerocool PSU should be far better than Seasonic PSU, right?
But that is not the case.
What determinants the good PSU is the internal components used in it (e.g capacitors). Since Strike-X 1100w PSU is built by Andyson and it's using low quality components, it isn't reliable PSU and hence why it's low quality (Tier four) PSU, despite looking fancy. S12II-520 is built by Seasonic itself and it uses almost the best quality components in it, while still being affordable to the majority of people and hence why S12II-520 is good quality (Tier two) PSU, despite lower efficiency and plain looks.