Addendum: Corsair's new RM Power Supplies
Corsair is also launched a new line of power supplies alongside the 750D, the RM family. Why RM? Not sure. Near as we can tell, it doesn't stand for anything in particular.
Like Corsair's other high-end PSUs, the Corsair RM650 retains the flat-pack cabling option.
So what do these new power supplies offer over other Corsair power supplies? Since Corsair's advertising and product webpage are short in details, I pulled together a full shot-by-shot comparison to show you the RM650 against the high-end HX650.
Here's the quick version:
The RM650 is fully modular, the HX650 isn't.
The RM650 has basic support for Corsair's enthusiast "Link" light/cooling management system, the HX650 doesn't.
The RM650 can supply up to 130W across the 3.3V and 5.5V rails compared to 100W for the HX650.
The HX650 uses a different type of bearing in its fans.
The HX650 spins up its fan at 20% load, the RM650 spins up at 40%.
The HX650 has a maximum fan RPM of 2200 vs 1,050.
The HX650 will output 46.9 db(A) at full load, versus 24.8db(A) for the RM650. That means the RM650 is much, much, quieter.
There's a final set of differences not listed above -- the RM650 has significantly longer PCIe cables, at 750mm, up from 600mm. Unfortunately, the main power and ATX12V cables, which often could really be useful if they were longer, remain the same length on both units.
So far, all these changes favor the RM650 over the HX650. The final caveat, however, is that the warranty period on the HX is 7 years, while the RM is just five. Most people probably don't cash in the warranty on their power supplies, since it's a unit you tend to need immediately. If you like the increased tolerance and quieter fans, the RM650 is worth considering.