I’d like to run 100V equipment here in Australia, is this an issue?

Not at all, as long as you have a quality step-down transformer of the correct power rating.

Such a transformer should be from a quality local manufacturer, like Tortech. It should be rated to deliver 1.5 to 2x the rated maximum power consumption of the attached equipment. Obviously, if you have a big powerful amplifier, you’ll need a really massive step-down transformer to power it. For low powered equipment like turntables and preamps, a small transformer will be fine.