FYI this is one of the last batch of 05's (Built date 05/05). The 06's went in production in 06/05. So like many other XFs it sat somewhere for 14 months before the first owner took delivery. I wouldn't worry too much about it at this stage. If it had any storage related problems, they should have been taking care of by now.
IMO price is on the high side for an 05 with a 6 speed, I would negociate for some extended warranty and/or some maintenance to be included. Oil changes are expensive on this car.
good luck