A better option than wifi for xbox live or any other Ethernet via wifi connection you need to make.
Electrical power is supplied and distributed around your house at 50Hz. However, the wires are actually capable of carrying a range of other frequencies which can be 'tuned-in' using appropriate equipment. Powerline Homeplug technology takes advantage of this unused bandwidth of the electrical wiring in the home.
The signal can travel between floors of a house even when they are on a different ring main, as long as they are on the same consumer/fuse-box your side of the meter.
Works with just about anything with an Ethernet port and is driverless unless you need the encryption utility (supplied on CD-Rom with each pack).
PC, Mac, Linux, PS3, Xbox including Xbox 360 and media adapters/players. all just plug in and are away.
If you do manage to find an Ethernet device it will not work with you are welcome to send them back for a full refund. No quibbles.
Fully homeplug 1.0 compliant so will work with all other 14mbps & 85mbps compliant plugs.