Remember that curious search result for a "Radeon RX 500X Series?" Mystery solved. Today, with no fanfare whatsoever, AMD released 5 new graphics cards in the Radeon RX 500 series lineup. They are the RX 580X, RX 570X, RX 560X, RX 550X and RX 540X. Don't get too excited, though, because there is literally nothing new about these gaming GPUs except for the "X."
Not coincidentally, HP just launched a new lineup of Pavilion gaming laptops (to be fair, they're definitely priced to move and worth a look) and among them you'll notice something unusual about the GPU spec: a Radeon RX 560X.
The entire stack of Radeon 500X graphics cards is only available to OEMs like HP, Dell and Lenovo. You can't buy them at retail. That's because the sole purpose of slapping the "X" on the name is to provide these OEMs with something "new" to sell, fresh marketing materials and a renewed sales surge.