15A or 20A wall recepticles?

Which is best suited for 20amp breaker. This is for monoblock amps.

If you have a 20 amp breaker you need both a 20 amp receptacle and wiring between the breaker and the receptacle that's rated for 20 amps.
If you have only one outlet on the circuit, it must be a 20A outlet. For multiple outlets, it is permissable to use 15A outlets, but I generally use 20A outlets. If you have the capability, might as well advertise it, right? And I'm sure you're already aware that you need to use 12 ga wire.

Good luck.

Sufentanil has been sampling the goods again! Unless you have a really monster amp and I mean monsterous close to a 1,000 watts that requires 20 amps which consitute a tiny handful of the amps available, you will not pull 20 amps period.
Although most audiophiles including myself think it's better to have 20 amp outlets. I have big monoblocks on dedicated circuits which are 15 amp no problems and I also have a 4 outlet box on a "dedicated" line which is 15 amp total. It powers my souces and preamp again no problem.
If you can afford it get the multiple dedicated 20 amp lines. Then you can buy those used ultra hi end power cords cheaply because they have the funky 20 amp terminations that people have a harder time selling.
Even better get a few 220-240 volt lines and get the European and Asian stuff very cheaply. You can always attach a big appliance to them if you can't find the audio gear.
Mike how are you? any 6 footers?
No, Sfar, it is NOT required to use a 20A receptacle on a branch circuit rated at 20A UNLESS the receptacle is the ONLY one on the circuit. Why don't you test this in your own house: Kitchens required 2 20A circuits (GFCI-protected), and bathrooms require a 20A circuit (GFCI-protected). Go down and look at your electrical panel. If your wiring is reasonably recent, you will see 20A breakers for both and 12ga wire coming out. Now look at the outlets themselves. I'm willing to bet that at least some are 15A GFCI (or GFCI-protected by breaker or upstream GFCI outlet).

And to my buddy Steve, it's been a while. We'll catch up soon.

I hope that clarifies things, Kenbo.