I can't speak to the voltage converters sold specifically for that purpose which are typically autotransformers.
I can speak to the use of step up isolation transformers, which can substantially INCREASE the performance of components powered through them. Mains power here in NYC (and I assume throughout the country) sucks, and has a very negative effect. Step up transformers identified as 'medical' will have a shield between primary and secondary which attenuate high frequecy noise as well as minimizing common mode noise of all frequencies. Assuming they've a adequate va (wattage) rating, they will provide substantial benefits.
Another excellent approach, feasable only if you're confidant in your DIY abilities, is to implement your own balancing powerconditioner, ala the Felicia project -
http://www.audiocircle.com/index.php?topic=18443&highlight=the only change you would make is wire the primaries of the input transformer in parallel, leaving everything else the same, and you'd get balanced 230vac at the output with substantial powerconditioning applied.