Can I take American equipment to Europe?

Anything which is high-wattage will potentially be an issue (which may be why Jerico's wife had a problem). Hair dryers are about the most toxic appliances ever made. They consume at or near the recommended limit for many receptacles and one would need a mammoth step-down transformer to run one safely, and one that large would be so heavy as to be prohibitive to travel with.

Most audio equipment other than amplifiers are low-wattage. I don't know about your amps/speakers.

There are differences in transformers. Some hum. Bad ones hum a lot. Good ones don't. You can pay for quality. I note that some Japan-made ones are excellent. I use several for step-up duties (producing 120V from mains which give me 100V).

In your case, you will be stepping down, which is easier on transformers than stepping up.

You can find a PS Audio device which will switch mains frequency from 50Hz coming out of the wall to 60Hz output (I am using one now - a P300) however, to my knowledge, you will not find one which will both step down the voltage AND change the frequency generated. The only product I know which would do that is one VERY expensive version of a CSE power regenerator (CSE is a Japanese company), and that would cost probably $2000-2500, and probably would not do all your equipment - just some of it. Not all PS Audio power plants (notably the PPP) will accept a different input frequency (i.e. accept a 50Hz input and output 60Hz). The older P300, P500 and possibly P600 will, but they have limited current capacity, so lower power items such as preamps, CD players, and whatnot should work. Higher-power devices are perhaps best sent back to the mfr for a transformer change by the mfr. It may cost more than a cheapo transformer but it may also allow you to sell them used in the market where you reside (which may have a higher resale price than the US - especially given the condition of the dollar compared to the euro since you bought your items).

Remember the overhead required too.