Lehmann Black Cube SE ii with EU voltage - step up transformer

Hello all - recently purchased a Black Cube SE ii here on the ’gon and when it arrived, I discovered that it is an EU 240v version and not the US 120v edition I need. I admit I’m annoyed with the seller - this wasn’t made explicit in the listing, only evidenced in one photograph of the box. Given the fact that we had multiple exchanges prior to purchase and he knew my shipping address was in the U.S., well, you’d think he might have mentioned it. But, well... there was one photo among many that I did not think to scrutinize. Another lesson in buyer beware.

Anyway, I am now trying to decide whether to return the unit or use it with a step-up transformer that will take my wall voltage of 120 and convert it to 240. The Cube SE ii draws an MPC of 7w, so it is not a power hungry little bugger at all, and should function fine with a such a device. My question is... will it affect performance? Will I be getting the full effect of the unit? Have any of you used EU 240v devices with such a transformer as a long-term fix and were you happy with that arrangement? Thanks for any input.