Conclusions
We've covered a lot, so before diving into our conclusions on each power supply we've tested, we should take a moment to note some general trends. With few exceptions, all the PSUs in this round-up are pretty good. In fact, only Cooler Master's 650W Real Power Pro failed to deliver tight voltage tolerances, and then on only one rail in our 100% output capacity test. Ripple wasn't much of a problem for these PSUs, either. ThermalTake's Toughpower may have been the worst, but its average AC content was well within acceptable limits. Heck, even overall efficiencies were impressive. The lowest efficiency we observed was 76.7%—just 10 percentage points shy of the highest.

So brand-name PSUs are pretty good in general, it seems. Some are better and worse than others, of course, and to help you sort through this litter we've provided a quick summary of our thoughts on where each stands.

Antec EarthWatts 500W — By far the cheapest PSU in this round-up, the EarthWatts looks to be good value for budget-minded environmentalists, especially since its power delivery is solid. Despite leafy-green goodness, the EarthWatts isn't the most efficient PSU of the bunch. It isn't that quiet, either, and that pokey 80mm fan has doesn't move a lot of air. You're better off saving a few extra dollars for the next PSU on our list.

Antec Neo HE 550W — The Neo HE is a great example of how spending just a little more can pay huge dividends. For less than $20 more than an EarthWatts, you get a five-year warranty, efficiency that's nearly as good, modular cabling, and an additional 50 watts of output capacity. Only the Neo HE's relatively high noise levels keep it from an Editor's Choice award, but it's good enough for an effective silver medal, our TR Recommended designation.

Antec TruePower Trio 650W — A five-year warranty and 650W output capacity start the TruePower Trio off on the right foot, but it doesn't offer much in the way of luxury. The Trio lacks modular cables and 8-pin PCIe connectors, and it's far too loud given its $120 street price. Spending a little bit more will get you a significantly better power supply.

Cooler Master Real Power Pro 550W — The Real Power Pro wasn't particularly exceptional or disappointing in our testing. Like most of the field, power delivery was good, if not great. While the others were able to distinguish themselves with high efficiency, low noise levels, or cool system temperatures, the Real Power Pro spent most of its time at the middle or back of the pack. Without a long warranty or modular cables to add to its appeal, the Pro just isn't compelling value, at least not while it's selling for $95 online.

Cooler Master Real Power Pro 650W — This 650W flavor feels almost like Cooler Master pushed the Real Power Pro a little too far. The sagging voltage we observed on the 12V PCIe line under 100% load is enough to quash any chance we'd recommend this model, particularly given the strength of the competition. Even if it had managed to maintain adequate voltage on the 12V rail, the 650W Real Power Pro would still be as average as its 550W brother.

Corsair HX 620W — Buying into a company's first stab at a new class of products is rarely a good idea, but Corsair's first entry into the power supply world is worth an exception. The enthusiast pedigree shows. With a five-year warranty, the best modular cables we've seen, dual 8-pin PCIe connectors, and among the highest efficiency results and lowest noise levels, the HX 620W is arguably the best all-around PSU of the lot. Overall goodness isn't cheap. In fact, it costs just about $140 online. We think the HX is worth every penny—and worthy of an Editor's Choice award.

Enermax Infiniti 720W — A nearly $200 price tag makes the Infiniti the most expensive PSU in the round-up, and that sets expectations high. For the most part, Enermax delivers, equipping the Infiniti with a massive fan that's quiet under load, 720W of output capacity, and modular cables. Yet the whole package doesn't quite come together, in part because the Infiniti's comparative efficiency is so low. Given the competition, we'd expect a five-year warranty at this price point, too.

OCZ GameXStream 700W — With a $115 street price, the GameXStream delivers great value in terms of watts per dollar. Unfortunately, unless you're particularly partial to blue LEDs, there isn't much else to get excited about. In fact, the GameXStream's relatively low efficiency and high noise levels are a little disappointing. We can vouch for the GameXStream's reliability, though, and that counts for something. Just not quite enough.

PC Power & Cooling Silencer 750W — The Silencer lives up to the hype surrounding PC Power & Cooling, and then some. This PSU just about has it all, including a five-year warranty, clean power delivery, dual 8-pin PCIe connectors, and a truly monstrous 12V rail. Despite using an old-school 80mm fan, noise levels are remarkably low, as well. Throw in the highest efficiencies we've seen and you have our second Editor's Choice recipient. A quality power supply is an investment, and even at around $170 online, the Silencer is a good one.

Seasonic S12II 500W — The S12II is a very good power supply. Even a great one. Power delivery is clean, efficiency is excellent, and noise levels are pretty low. That's all you really need from a PSU, which is why we don't so much mind the lack of modular cables, the three-year warranty, or the relatively pedestrian 500W capacity. At least, we wouldn't mind if the S12II weren't so expensive. This model is scarce online, which is perhaps why the cheapest we've seen it at is $110. At that price, the S12II isn't a particularly good value. However, it's still a great power supply, one we'd heartily recommend should you be able to find it for less.

ThermalTake Toughpower 700W — There's a lot to like about the Toughpower, including its five-year warranty, 700W output capacity, and modular cables. Considering those perks, the unit's $150 street price looks pretty good. We can even forgive the Toughpower's comparatively high ripple content since it was well within the PSU's tolerances. We can't get past the noise levels, though. The Toughpower is among the loudest of the lot at idle and under load—a problem its direct competitors don't share.

And so The Beast's first run through a pack of power supplies comes to a close. Weeks of testing hasn't been kind to this lot, but it's given Corsair's HX 620W, PC Power & Cooling's Silencer 750W, Antec's Neo HE 550W, and Seasonic's S12II 500W the opportunity to set themselves apart.

Update 10/05/2007 — Cooler Master has bumped the warranty coverage of its Real Power Pro power supplies to five years. The longer warranty adds value, particularly to the 550W model, but it doesn't change our overall recommendations.