It should be fine.If you consider you have a 3amp fuse for a 120v line,if the amp were to draw more than 360watts for more than a couple seconds the fuse will blow,so the 750watt step down is okay,it sounds like overkill,but doubling the watts capability is a good safety margin,it is likely the amp could draw more than 360watts briefly on initial start-up,that is why it uses a slo-blo fuse.