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The SX700-G's price is high. But it's still more affordable than Corsair's flagship SF750. To be sure, you'll pay a premium for the most powerful SFX-based PSU out there. Moreover, the SF750 achieves a higher performance score, it comes with individually sleeved cables, it includes two EPS connectors, and Corsair bundles an SFX-to-ATX adapter bracket.
In terms of pure capacity, however, the SX700-G achieves a win by delivering more than 1kW before its over-power protection mechanism kicks in. While we'd prefer to see a lower limit on the OPP feature, it's still amazing that such a small PSU is capable of such high power levels without running into problems. It seems like this platform could be rated for more than 700W, though stretching so far would prevent it from satisfying the 80 PLUS Gold standard's requirements. A higher power rating would also result in more noise from a fan forced to spin faster.
At load levels up to 350W, the SX700-G's fan is quiet. Beyond 450W, though, it exceeds 40 dB(A). Acoustics like that are annoying to most users. We believe the fan isn't configured optimally; it should ramp up to higher speeds more gracefully. This is, after all, an efficient platform. It doesn't get especially hot, and the fan's diameter is a generous 92mm so we know it can move plenty of air at lower speeds. SilverStone's OEM must have wanted to be extra certain that the SX700-G would survive its (short) three-year warranty period. On that note, SilverStone should really arm its SX700-G with at least five years of coverage if it wants to keep pace with the competition.
Fundamentally, the SX700-G is just an overclocked version of the SX650-G that doesn't offer anything new. It comes with the same number of cables and connectors, and is only 50W stronger. So, if you don't want to pay a premium, the lower-capacity SX650-G is nearly as good. It even offers four PCIe connectors, whereas Corsair's SF600 only has two.
We'd like to see an improved version of the SX700-G with two EPS connectors, higher efficiency under light loads, and less than 30 dB(A) of overall noise output. Such a configuration would be a good choice for builders who don't want to pay Corsair's high price on the SF750.
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Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics, and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.
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Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.