20A IEC are used to enable a more secure and reliable connection to the component.
I actually completely disagree with this statement. I have 15A IEC connectors that actually make a better/snugger connection then even the 20A Furutech.
Basically, 20A IEC vs 15A IEC has to do with electrical component standards. This ensures that somebody does not use or connect a piece of equipment to an inadequate outlet/source. Generally speaking, a 15A outlet/connector is usually wired to only allow capable transfer of 15A. This usually means 12awg wiring. For 20A IEC, it is recommended to use 10awg romex wiring (although sometimes even 12awg is okay for a short run). Trying to wrangle 20A of current from a 15A outlet/wiring can cause the main circuit breaker to trip and/or cause possible electrical fires.
As far as current capability, a good 15A IEC connector can certainly carry 20A of electrical current. This is true for most of the good items such as Furutech or Neotech or Hubbell. However, be aware that there are several 15A cheap power strips or adapters that use very small gauge or thin metal for conductors.
If you want to change the 20A IEC inlet on your equipment, you can certainly do that. However, keep in mind that you are now violating "electrical standard" connections. It should not hurt anything if you use a good high current power cord and outlet. However, if you ever decide to sell the equipment, you can be liable for lawsuit if the new owner does not properly connect it to an adequate power source and results in fire/damage.
The Furutech FI-32(R) 20A IEC is actually not bad for $203. It is phospher bronze instead of pure copper like the NCF plugs. But it's still really not that bad.
Wattgate has a 350i HC Rh rhodium palted 20A IEC for $122. However, it's pretty much a multi-plated brass conductor, but definitely cheaper.