The official TSA rules are here... they do indeed specify that consoles must be removed from their carrying case. I'm not entirely certain that a retail box counts as a carrying case... if it's still factory-sealed, they may allow it, but I have no experience with that.

UA should allow it as a carry-on, though I'm not sure if it would count as your carry-on or your personal item...

That said, I don't think the recipient would mind horribly if it were opened. The factory seal is only a clear sticker. If you want complete peace-of-mind, the previous suggestion of shipping is a good one. You can do FedEx Home Delivery with insurance for around $20.