Here's the thing with grading: it's a total crapshoot. One grader may notice your minty console, and give you the most money possible. Another may notice you're missing the box, and boom, worst grade/worst money. Technically, no box means lowest grade, anyways.
Someone may pay more with PT on it, but you'd probably have to go to eBay, accept PayPal, and worse, keep the account tied to it.
If I was very interested in getting a PS4, I'd offer you the credit. Surely you can sell it here to someone you know for e-gift cards.