Luxman L-509Z Integrated Amplifier

Get a step down transformer.  Aside from wasting a bit of electricity it won't impact the sound quality. If anything it may actually help smooth current to the amp and add a layer of protection against an electrical surge. 

Paul probably means 10x continuous power, not peak power.  The 507z draws 86 watts at idle so using Paul’s math that would be about 860 watts for the transformer.  Another recommendation I’ve also heard that you want at least 2x peak draw, so in that case the 507 has a peak consumption of 350 watts which means you’d need at least 700 watts for your converter. I don’t have any brand recommendations but power converters are not complicated devices, and everything is made in China anyway so I’d probably get a generic model off Amazon with 1000 watt+ rating just to ensure additional margin of error for exaggerated ratings.  You can find them for less then $150 with your choice of Toroidal or El designs.  

Oops I just realized you meant the 509 not the 507.  The 509 draws 130 continuous and 370 peak. If you want to use Paul’s guidelines that’s 1300 watts.  Still easy to find under $150