I had planned on going to the King of Prussia store this weekend
Assuming that you cannot go to Philadelphia because you are sick, do you want to know what is at King of Prussia so that you ask our SCLUG reps to stop there for you? Otherwise, if you are planning to place an order over the phone, it does not matter WHERE you order the parts from because you will have to pay a flat fee of about ten bucks for shipping. So it might be easier to determine which store has the main part that you want and to order from them. My impression is that the Orlando store has the largest selection and that is who I usually call if I am placing a LEGO store order over the phone.