To be on the safe side, I'd recommend a 300W unit to be sure you won't overheat the transformer when used full-tilt in order to allow you to keep working however long you need to use it (takes into account power factor, and that the W ratings of the transformer are typically peak/max, not nominal).
And as you mention, it's useful for other 110 - 125V tools you may be able to get for less than their 230V mains versions.