ok... you probably got a simple case of defective cap.... most likely there is no more damage to the the unit . you need all 4 caps to be replaced and that is probably it ...
Beware of NAD M3 Fire Hazard
My $3k NAD M3 started shooting sparks out the top and burned the shelf that was 8" above. Luckily I was home and not sleeping or the house would have burned down. If anyone has one of these I advise them to unplug it when not in use. I took it to two different repair shops and they said it would be about $800 to just get it running and there may be board issues. They advised not to take the gamble. Anyone have any suggestions on what to do with it?