HTPC PSU advice required

[Carbon Copied]

Just looking for some advice on PSU choice - currently building a HTPC / 24/7 on media server with the following components:

9 WD Red 6TB HDD
i5 3570k (stock to light overclock with h100i cooling)
16gb Samsung Green

for what I need power wise I'm guessing a 660w PSU (namely the Seasonic Platinum Series V2 660W) will be sufficient for these initial needs; however in the future I'm looking to potentially add a 970GTX for gaming in the living room. My questions are:

- Is 660w enough or would it be better to use a 760w to provide the bigger overhead when the graphics card is added?

- Will the platinum rating make that much of a difference compared to the gold varieties (I ask this as the 650w Superflower Leadex Gold is on sale currently at OCUK and may be an alternative) - I understand that it's all about efficiency but from what I've read online it seems to only start making tangible differences to the more higher 1000w+ being taxed 24/7 and the HTPC will only be taxed once the graphics card is in and actually running games.

Any advice would be appreciated.

 

[Carbon Copied]

Much appreciated for the response Chug - so with more than enough juice at 660w for my needs I take it the 650w Superflower Leadex Gold will be a more adequete contender for hitting that 50% magic number, as components won't be stressing it enough to take advantage of the "platinum efficiency" in other PSU's?