I just upgraded to the Sapphire nitro+ RX 480 and was planning on selling my old Asus HD 7870 GHz edition. I've looked online and I've seen REFERBISHED ones for $175 and some new units up to an outrageous $500. This cant possibly be correct. What are some opinions on the cards worth? It is used obviously, never OC'ed and kept cool in a well ventilated case. Just don't wanna rip anyone or myself off.