An XBee would require a lot of surrounding electronics to transmit and receive data, namely an ADC and MCU on one end (16bit minimum, 24bit if you want "pro" audio), and another MCU with a DAC on the other end. Chances are that you'd get bits of jitter at times, causing your music stream to sometimes glitch. Wifi channels start at 2412MHz up to 2462MHz in steps of 5Mhz. The link you provided on ebay works on a choice of 4 channels, 2411Mhz, 2431Mhz, 2451Mhz and 2471Mhz. With the link you provided having spacings of 20Mhz, this makes me assume that the whole link requires a 40Mhz bandwidth (makes sense if its transmitting video I suppose). Unless your router is operating in the higher channels, you could probably get away with the 2471MHz channel. I couldn't tell you if you'd get interference or not however.