The H/K 3480 is a great unit for the $.Adding a sub to that reciever will not take a load off the reciever as the receiver has no crossover unit to it so it will still send a full range signal to the speakers.

If I were to start a 2 channel system I would go the amp preamp route unless you listen to a lot of radio.Even though the 80s are a sensitive speaker they really do like the power put to them.I would go for a 200 watt amp of good quality and a matching preamp.For now I would forgo the sub and add it at a later date if you felt the need for it.
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Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud