In these days of the global economy most electronic equipments have power transformers with windings for 120 and 240 volts (sometimes more). Some equipment already has both windings connected, with a selector switch to be set according to where you live. If there is no switch, it's easy to disconnect the 120V winding wire and connect the 240V wire. The power cord wall plug will also need replacement to fit the 240V socket.
As to sound degradation due to transformers...I hate to tell you how many transformers your power has already been through before it gets to your house. Transformers are not evil! (except in the audio signal path). A 240V to 120V step down transformer adequate for high power amplifiers will be big, heavy, ugly, heat-producing, and not cheap. That's why it would be best to use any 240V capability that the equipment already has built in.
By the way, we have 240V here in the good old USA...that's what your stove, clothes dryer, well pump, air conditioner, etc runs on. Instead of buying power line conditioners, perhaps we should all be wiring up our audio equipment at 240V.
