I'm surprised the Classe doesn't have both XLR and RCA. If it does offer both--then just use the RCA--but if that were the case then you probably wouldn't have asked this question. You can go XLR to RCA pretty easily. I would recommend that your interconnects be relatively short (less than 2 meters). All you have to do is use one of the hot leads (positive polarity) and the ground from the balanced end to the RCA. To check the pin configuration it should be in the Classe Manual. If not you can call Classe and find out the pin configuration. The polarity is reversed on some manufacturers units--I don't know about Classe.
Also, there are adaptors made for this, but I know little about these--perhaps someone else knows about the adaptors.
Also, there are adaptors made for this, but I know little about these--perhaps someone else knows about the adaptors.