Okay...this is a very wide open topic with PLENTY to learn about. Ok, so u want to compete? like spl competition? if so, you need to know what ur getting urself into...plenty of money, plenty of time, and u REALLY need to learn a lot...i mean as much as u can b4 you jump into it. I've been on this forum for like a year and a half, and i finally think i know enough to compete somewhat successfully.
SO, cruise the boards. what is ur budget? will this be your daily setup also, or just strictly competition set-up? what type of vehicle do u have? Also, i wouldn't go with tons of 10s...maybe 2 12's...one 15 or 18....u need to look at what organization (dbdrag, nspl, usaci, meca)hosts a lot of competitions in your area and decide which class you want to compete in.
a few companies to look at are:
Resonant engineering
http://www.respl.com
amps: tru-tech, orion, mtx, mmats
also, u'll need to possibly plan for electrical upgrades...most likely at least a 200 amp alternator (minimum...)
http://www.execessiveamperage.com and an optima yellow top battery.
good luck, tell us what ur looking for and we can help ya get started. peace
NG