A step-down isolation transformer is actually a type of power conditioner that helps shield noise from your AC power lines. This will likely improve sound quality overall, so you can definitely do something like this. Actually, many power conditioners use a big isolation transformer as part of it's conditioning.
I have a friend in the UK and he's used the Bronson step-down transformers on audio equipment with a lot of success. The 590AXII is not that demanding and only uses about 330 watts max. I would look at a Bronson++ VT 2000 or a Bronson++ VT 1500. You generally want a larger transformer so that it does not have to work as hard and give better current delivery. You can get these on UK Amazon site or from various locations around Europe.