I would make sure to either buy your iMac directly from Apple online or
using 1800MYApple by phone or at a local AppleStore.
I would not buy at Comp USA.
I wish I didn't feel so strongly about Comp USA, but they've pulled a few fast one's on uninformed buyers selling them previous models when new one's were available. They also sold open box items as new.
If you have a family member or friend that can help your parents use the
education discount, then by all means save some money.