This article is from the Car Audio FAQ, by Ian D. Bjorhovde (email@example.com) with numerous contributions by others.
This section is mainly geared toward IASCA.
There are three classes: novice, amateur, and pro. The novice class is
intended to be an unintimidating level where beginners can start out;
however, a competitor may only be in the novice class for one year, at
which time he is automatically moved to the amateur class. Most
competitors stay in the amateur class indefinitely, unless they become
affiliated with a car audio shop or manufacturer, at which point they
are moved into the pro class.
Are you or were you employed by a car audio manufacturer or dealer?
You compete in pro
Is this your first year of competing?
You compete in novice for the first year
You compete in amateur
Note that modifying your amplifiers, buying your equipment below
retail, or being sponsored by a manufacturer or dealer will get you
kicked into pro.
Also note that any home built active gear in the signal path (e.g.
custom built equalizers, crossovers, or noise gates) will get you
kicked out of novice.
Once you know what group you are, you next need to know what power
category you are in. Add up the 4-ohm non-bridged rating of all your
amplifiers, including your head unit if your head unit is powering
speakers (rather than exclusively feeding amplifiers). Then, find the
category you fit into:
Novice 1-150 151-300 301-600 601+ Amateur 1-150 151-300 301-600 601+ Pro 1-150 151-300 301-600 601+ Expert 1-600 601+