use my wave system as speakers for another amp

You could connect the preout of the receiver to the aux in on the wave radio. This is OK just as a temporary way of using the receiver but you won't appreciate it until you get some real speakers. Find some used ones if you can afford to get something decent.
 
Almost certainly yes. My 15 year old Bose Wave (I inherited it) has AUX inputs. AUX output from the Onkyo, done.
 
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