Amplifier voltage conversion

I am interested in buying a processor-amplifier combo in the US and taking it to Europe, i.e. Anthem D2v+P5 or Classe SSP-800+CA-5200. Now obviously there is a voltage and hz difference between Europe and US and transformers seem to be a no-no from a sound quality perspective unless one goes for industrial/medical instrument quality products.

Now there is the option of voltage conversion by various audio shops. Now I am not veyr techie unfortunately and hence I would like to ask if anybody can explain me whether this voltage conversion has any negative benefits and what exactly is changed?

I mean is it the whole transformer that needs to be replaced (unlikely some audio shop can do that) or is it just a fuse or a switch(can even be done by a knowledgeable amateur without degrading sound I would assume)?

If it is very different between manufacturers I would be in particular interested in Classe and Anthem amplifiers and processors.

Thank you for you explanations!