Higher amperage doesn't matter, it will only take what it needs. It's more like the maximum amperage that the adapter can supply, systems won't always use as much current as the adapters list. The thing is while some Genesis Model 1 adapters output 10V, most seem to be rated 9V. They changed the adapters during production of the Model 1s, so his might be slightly underpowered to run the Famicom properly.