i'll assume your XB is NOT a late 2009-2010 with the 3 bearing rear wheel hub/axle design:
1-all balls kits are very nice for both front and rear hubs. i stock them and sell alot to board members.
2-all the major quality brake component manufacturers make XB F&R pads. i prefer EBC HH and sell alot of them to board members.
3-EBC offers a reasonably priced top quality replacement rotor with different surface hole appearance to it for around $165 or so. there are also a few wave-rotor styles availble from ferodo, etc.
4-tensioner pulley requires 2 bearings. part # is 6203. available most anywhere. BUY QUALITY! these things handle quite a bit of load.