jls do not need a birthsheet once you hook it up you will agree they deliver way more than they claim a buddy of mine has one 10inch w7 powered by a 500/1 and it hits hard than most 12's. i know my 500/1 put out a sh1t load of power i had it poering 3 w3s and still had it turn most the way down. the point is i've had a couple different amps and after own jl i will never own a different brand they are indestruckable and deliver way more power than they claim to. jls may be more expensive but i view it as you buying an anp that you will not be dis-satisfied with and i know i will own mine for years, go with jl and you wont be disappointed