As Ranger noted, this is defined by code. However, there is a different spec for 15 (typical for home) or 20 amp service, and/or if you want isolation grounding (has extra ground wire). If you are putting in a dedicated circuit for your AV stuff, make it a 20 amp circuit with isolation grounding (typically comercial). Any decent electrician knows what the this means, knows your local code, and knows about isolation grounding (just ask him/her). They may look at you strangely because 20 amp IG circuits are commercial, but stay firm, they will install them for you. One just cost me about $100 for parts and install.