Re. Marantz Receiver Capacitors

If the unit has been in semi constant use, your cpas should be fine.  You can try and reform them if they look good by bringing them up slowly on a Variac.  I’m not a fan of recapping just because the caps are old.  If they are defective or measure poorly then yes, replace them.  Once they start to dry out they bulge and the cans will begin to leak. 
You might also hear some hum when the unit is turned on without a source playing.  That’s a good tell tale sign the filter caps are on their way out.

Sometimes they expand with age and begin to bulge and the tops look somewhat rounded. These would be bad. But the age of these caps should be replaced regardless. Better safe than sorry.