ticking noises associated with hard disks are never good
maybe you should hook it up a PC and run S.M.A.R.T. diagnostics and/or the western digital diagnostic utility. If you find anything reported, return the disk.
Anyway, keeping HDs near magnetic fields is obviously not recommended, however the HD itself is shielded enough to protect itself from relatively weak magnetic fields. Your TV is more at risk than your data, provided the xbox is >0.5m away from the woofer magnets.
Also the xbox shielding does a pretty adequate job of neutralizing fields on the inside...
If you're still worried, try to keep the xbox off the axis of the magnets, where the magnetic field is significantly weaker.