There is absolutely nothing wrong with using 20 amp breakers as long as you run 10/2 wire.
Yes, there are preamps and amps constructed for 20 amp IEC's, it is possible that if you use a 15 amp breaker the product might lack its full potential.
If you are going to use an HFC Hemisphere then I would suggest you use a Furutech GTX-D NCF (R) outlet and not the cruzeFIRST Maestro outlet to power the Hemisphere.
Yes, there are preamps and amps constructed for 20 amp IEC's, it is possible that if you use a 15 amp breaker the product might lack its full potential.
If you are going to use an HFC Hemisphere then I would suggest you use a Furutech GTX-D NCF (R) outlet and not the cruzeFIRST Maestro outlet to power the Hemisphere.