Myth 1 : A motherboard with more power phases gives you better gaming performance!
This marketing mumbo-jumbo peeves me a lot since many poor blokes are going to part with 6 months worth of wages merely because the box or advertisement claims "better gaming". The truth is more power phases will never improve a motherboard's gaming capability or your own performance, for that matter Hell, it’s not an assurance that the motherboard's power delivery is going to be good.
Let me give you an analogy. Would you prefer to hire 4 well-trained workers who can do the work efficiently and won't slack off, or would you prefer to hire 6 or 8 part-time workers who are not only poorly-trained but are also slackers? When it comes to motherboard design, it's not the number of phases that matter. It's how well they were designed in the first place, and the quality of the components used.
Good motherboard designs will be able to deliver stable voltages, even with fewer power phases. Having more phases will not necessarily mean the motherboard will not droop or fluctuate in voltage when you subject it to a large load. Voltage droop and fluctuations will not only make the system unstable, but it will also reduce the lifespan of your PC components.
So, how do you know which motherboard has a good design? Do your research - read reviews and feedback by those who are serious about their motherboards. When I mean serious, I really mean folks who are armed with multimeters, power analyzers and take a darn long time to study each and every aspect of the motherboard. As such, their feedback do not come right after a product is launched. Usually, you have to wait a few weeks or months.
When it comes to motherboard reviews, it's often best to take initial reviews (released during or soon after the launch) with a pinch of salt. More often than not, they tend to be cherry-picked samples. The actual retail units may not yield the same results. You should try to get as much feedback from actual users of the retail motherboard before buying.
Myth 2 : Our power supply deliverx XXX "true watts" thanks to our multi-YYY technology
This is a similar case to the previous myth and occurs almost as often than not. Worse, some people actually believe that the more watts a PSU produces, the better it is. However, that is not really true. Good engineering is again the key point.
Cheap PSUs can attain "high" wattages at low cost by delivering most of the power output in the form of 5V. However, they are generally not capable of handling high loads on their 12V line. Good PSUs actually provide 12V lines with greater stability and load even though they have a much lower power rating. It's really not about the wattage.
So, it would really pay to do a little research and read up on the power supply you want to buy. You will find that some brands are noted for paying more attention to marketing babble, than actual engineering. You would do well to avoid them. Of course, even notable brands have been known to cut corners in some of their models, resulting in rather high rates of failure.
In short, forget about brand and power rating. It really pays to do a little homework before you buy your PSU. If you need advice on a particular power supply, or recommendations on a good one, try asking in our forums.