If a certain Mo.Bo. / CPU require a certain output power from the Power Supply (which they do nowdays), and that requirement is met, other problems such as Current Draw should be non-existent, since;
P = IV , or Power(P) equals Current(I) multiplied by Voltage(V). And the voltage is always constant for a particular output from the power supply, this implies that a certain component cannot pull too much current while operating at its given Power rating.
So I still say the same thing, power is power, if you need 300W, buy the cheapest 300W P.S. you can find, if you need more connectors, buy splitters, and as long as you dont go above 300W you are fine.
If you've ever looked at DC power on an oscilloscope with the Y axis set to voltage and the power source from a battery, you'll notice the waveform is perfectly straight. There are no ripples, quarter-wave or half-wave (etc.) artifacts.
Take a one of the simplest inverter circuits made up of 4 diodes and connect an AC source to the 2 input leads and connect the oscilloscope to the other two leads. You'll notice DC made up of half-waves, all on the same side.
Now take a switching power supply used in a PC and do the same thing. You'll notice that various brands of power supply provide varying levels of "pure DC" current. You'll notice variations in noise patterns, different amounts of bumpiness to that ideal straight line battery-provided DC current.
Under load, you'll notice even more variations. When one power supply is supplying 1/2 of its rated power, you'll notice some don't keep the voltages steady (V is not constant in the real world). One will provide nearly 3.3 volts on it's 3.3 volt leads, but when under 1/2 load (typical of many PC's), it dips down to 3.1 volts while another stays damn near 3.3 volts even at 1/2 or 3/4 load.
There are numerous other examples where power supplies designed to minimize component cost and those with a bias towards sound engineering principles differ.
But DC current definately comes in many flavors. I like mine smooth vanilla. Maybe rocky road is more your style, but hey, to each their own.