If the amp is for a sub and you have the money you should defiently go with the sub amp because It will provide a clean low level mono signal which is what subs are made for. Also it will be a lot more powerful than a multi channel amp where the power is broken up into many chanells. Sub amps also have the right resistence for the subs in ohms.

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.