I might be inclined to agree with what others have saidhere. I'm always looking for an excuse to upgrade a bike but you have toconsider the purpose of the bike when you weigh the value. For a commuter bike,I would be more inclined to keep it in dependable running condition at thelowest reasonable cost(highly subjective). Commuter bikes are exposed to moreinclement weather, potential theft etc. so I would be more inclined to repairrather than upgrade.
That said, if money is not an object, the process can be fun. The X5 shifter isthree speed for the front so you would have to set the limit screws accordinglyand just let the lowest gear position be two clicks since the granny ring willnot be present.