Could well be, yes. 600w divided by 12 volts = 50 amp draw. Most cars' alternators aren't designed with 50 amps excess capacity, which means the added draw will drain your battery until it is dry if you're busy rocking out all the time.
You need advice from someone who is combination mechanic and electrical guru -- i'm not even sure there is an alternator designed for the Echo that would support your added 50 map draw. However, there maybe is an aftermarket alternator that will do the trick and fit your mounting bracket -- after all, guys have been putting tunes into cars for a long, long time. Btw, don't rock out while driving at night until you get this sorted.
Your headlights need plenty amps, too.
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