i think the "e" series was the first line that JL came out with. They are probably good but they dont have that feature that makes them put out the same output from 1-4 ohms on them. This kid at work has a couple of them hooked up to his system but his faking car rattles so much i couldnt really hear if it sounded good.
the JL "E" series came out long after the "Slash" Series amps. theres really no comparasion between the "Slash" and the "E". the "Slash" series are some of the bast amps you can buy. the "E"'s just give you a little more flexability with the output since they don't use the R.I.P.S. system to regulate the inputs and outputs.
the "E" series is also going to be replaces with the "A" series sometime. JL always announces stuff, then it comes out a year or more later, even though i think they said the new amps were comming out this summer, lol.
The Slash series has many benefits but the major ones are the regulated power supply from 11.5v-14v and the impedence is good from 1.5ohm to 4ohm which doesn't effect(lessen or increase) power ratings.