So, the power plugs you are looking at are typically referred to as IEC type plugs, or 'D' plugs. They are industry standard and are the same ones which are used by many major televisions and projectors, as well as computers. So, in electronics, the IEC plug is king.
Understand that the wire gauge, which should be written on the outside of every one of the cords, is using American Wire Gauge (AWG). This means that smaller numbers equals thicker wire. So, 14 is thicker than 16. The three most common AWG sizes is 14, 16, and 18. Typical power in your home is run over 14AWG wiring. So, that's a full circuit with a dozen lights or many plugs in your home running off of it. So, rest assured that you aren't really likely to have any issues with any of the power cords which are drawing a fair bit less current on them in your home theater setup.
Yes, the amps will pull the most. This means your B&K amp, not the Nakamichi stuff. The Marantz if you ever hook it up. And, the subwoofer. If you are using the Sunfire, then definitely use the 14AWG on that one as the amp in that sucker is a very good one and may appreciate the extra capacity the heavier wire gauge offers.
Be very aware in this industry that plastic/rubber is cheap, and copper is expensive. A common ploy by many manufacturers is to increase the insulation around a slimmer cable to make it appear thicker than it really is. Neat trick, but still just a trick. It is the AWG rating which is what matters and 12 is thicker than 14 is thicker than 16 is thicker than 18, etc.
