A quick look through the service manual (available online) shows that your NAD needs to be manually re-wired. It shouldn’t cost an arm and a leg to get it done by a decent technician. You can do it in the USA and then use a voltage converter until you move (you can find the converter on Amazon -- I recommend the Krieger brand, as they are solidly built and UL listed).
Alternatively, you can just use the voltage converter overseas to convert 230V to 115V, and plug your NAD into the converter. No rewiring needed, and the 50Hz vs 60Hz should not be an issue. A much better alternative if this move may be temporary.

