I thought I read the PC&C PSU's didn't like modular because they believed it was another possible spot for connection problems and they preferred to use non-modular designs. I can see their point about it, however, I've never seen PSU problems develop at that connection point. I enjoy my modular cabling as I don't have to have more that what I need running in the case.
Agreed! PC&C is owned and made by OCZ some of the best memory out there. I have spoke with their Sr techs and most of them dont use the Single rail systems. The nice thing about single rails is you have all the amps available for that rail in one place. The disadvantage to a single rail system is overloads, noise and if a PSU failure happens you could lose your whole system and not just a GPU, CPU, Memory, HD etc but all of it.
A power supply is just as your house's fuse box includes both a large main breaker and a smaller circuit breaker per circuit to ensure the smaller branch circuit wires do not overheat, high-capacity PSUs divide their output into multiple "rails" each with a smaller current limit. The relevant safety standard requires a 20A limit (which a lot of manufactures ignore esp PC&C, they have enough amps on a single rail to kill ya), which is quite generous, given that the wires are smaller than those used in your house to carry 15A. (But there is the advantage that the wires aren't hidden in walls, so they're cooled better and you'll smell it if something starts burning.) This, however, makes connecting the PSU more complex; in addition to not overloading it overall, you have to avoid overloading each rail or it will shut down. A good power supply will make that easy by providing rails totalling much more than the total PSU rating. A cheaper alternative is to provide just enough rails to total the overall capacity, which makes it difficult to use all of a power supply's capacity. (This may be a clue that the PSU is incapable of delivering its full rated capacity.) An even cheaper alternative, which has become quite popular, is to eliminate all of the safety circuitry and produce a "single-rail" power supply which can deliver all of its output on any wire. This is technically in violation of the ATX power supply specification but has not proved to be a safety problem in practice, and is preferred by many people. A single-rail design is not itself a sign of a low-quality PSU.
Get a modular PSU if possible, as it will help eliminate extra wires to get in the way of cooling. Ignore the claims by PC Power & Cooling that modular cables create more resistance due to corrosion of contacts. The additional resistance is negligible.
A single 12 volt rail PSU just has one output circuit which generates 12 volts. All the various connectors which supply 12 volts are hooked to that one output. This kind of PSU will work just fine with a modern computer as long as it can deliver the wattage. That's true even if the motherboard requires the extra 4 pin or 8 pin 12 volt CPU connector or if your video card requires the 6 pin PCI-Express connector. As long as your single 12 volt rail PSU has all of those extra connectors and sufficient wattage then things will work properly.
Multiple independent 12 volt rails PSU
A multiple independent 12 volt rails PSU has more than one 12 volt rail. Each of the 12 volt rails has its own separate circuitry. Each of the 12 volt power connectors on the PSU cables is hooked up to one of the 12 volt rails. Since this is merely a PC PSU rather than a "real" one, the manufacturers often don't feel obligated to tell you which connector is hooked to which rail.
One reason to have multiple separate 12 volt rails is to improve the load regulation and noise on the rail. When you connect an active load to a voltage rail you tend to end up with a noisy rail which jumps around a lot. It's not a nice flat voltage. It varies. The more active loads you hook to a rail the messier it gets. So building a PSU with independent 12 volt rails improves the "cleanness" of the power on each rail. Normally this is only done if you have some circuitry which is extremely picky about the quality of its voltage rails because separate rails cost more money than a single rail.
By the way, in case you're ever tempted to hook the independent 12 volt rails together (I've seen people on the Internet who think this is a good idea), don't do it. Your 12 volt rails may have different ideas about what voltage they should set their rails to. One may be quite a bit different than another. They're separate rails, after all, and they have their own circuitry which controls the voltage. They're bound to vary a bit. And if they're just a little different then you can draw lots of current when you connect them together because each of the output circuits try to force the voltage on the same wires to a different value. That causes either a nice orderly shutdown from the over-current protection or smoke and sparks. There are some power supplies which have switches which allow you to gang the rails together. Once you've set the switch properly it's okay to connect them.
To properly compare power supplies, wattage claims must state the maximum ambient temperature for continuous, full-load operation. Unfortunately for the consumer, this information is usually withheld, opening the door for manufacturers to exaggerate their wattage claims. They do so by assuming an unrealistic ambient temp of only 25°C (77°F), even though the actual internal power supply temp is at least 40°C (104°F). Since the proper full-load rating is 15°C higher for home use and 25°C higher for industrial use, these power supplies produce 33%-50% less power than their advertised ratings.
Conclusion, if you think you need a 650 get an 850 or more. I do use in my builds modular and multi rail PSU's. We use them in Overclocking competitions and in everyday use. I feel its been proven to me that multi rails are better then a single rail. Currently PC&C is the only company making single rail PSU's that I am aware of. If this is such an improvement over multi rails why is there only one company doing this oposed to the many makers of PSU's
