Is a 750w quality power supply over kill? Yes it is and hurts absolutely nothing. It will do the job needed with ease. It will do the job and run cooler, quieter, and longer. Plus give room for the OP to add things to the computer later if desired without buying another power supply.
You may not know this, but a PSU like the 550W SeaSonic G Series powering a system that will have a maximum power consumption (
maximum, I said) will definitely run cool, quiet, and easily past its warranty. It'll probably easily approach 10 years. We're not talking about weak PSUs here.
So you see?
Tell any real PSU expert that you recommend a quality-made 750W PSU to power a system that has just two 670s and an i7-970 at stock, and they will have a good laugh and then they will tell you how that is unnecessary overkill and a huge waste of money.
Like I said, a quality-made 550W PSU is plenty, and you can get a high-end modular PSU for
$89.99 shipped from Newegg ($50 less than the overpriced HX750):
SeaSonic G Series SSR-550RM 550W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS GOLD Certified Modular Active PFC Power Supply - Newegg.com
This PSU can deliver 550W 24/7, even if its internal temperature reaches 50°C. A power draw of 450W would be a walk in the park for this PSU.
Good then go purchase it. My Daughters PC is 5 years old and it came with a 550 Watt PSU .Good luck with overclocking that. I hope it works out for you. I would pay no heed to anyone that would laugh at me.
A 550W PSU that comes with a computer is usually garbage and should never be trusted - especially not for overclocking. Although again, I'm not talking about overclocking and I never was. Just because the site's name is Overclock.net and just because I recommended that Layback Bear go over there to ask about me, it doesn't mean I'm talking about overclocking.
Anyway, the kind of PSU that came with her computer likely has very cheap internal components and its +12V capacity is probably between 250 and 300W (because it's 5 years old, and therefore it has that old design where the +12V wasn't nearly as important as it is today). For a modern system, that would mean it's a crappy 350W PSU at
best. It probably also has an extremely low efficiency of 70% or lower. I wouldn't even use a PSU like that in a simple office PC (a modern one).
The 550W SeaSonic G Series is a very high-end
modern PSU that has a +12V capacity of 540W. All of its internals are very high quality which means you could overclock with complete confidence. This isn't the only high-end 550W PSU, but it's a high-end modular PSU at a great price of $89.99 shipped. That's why I'm mentioning it. I could just as easily mention the 550W non-modular Rosewill CAPSTONE Series. It's essentially the same type of quality, only the PSU that Rosewill used to create it is the Super Flower Golden Green which is another awesome unit. However, it's $90.98 after shipping and again, it's not modular.
So you see, just because you have two PSUs with the "550W" rating, it doesn't mean they are identical.
