Newegg offers the MSI Radeon RX 480 8GB 256-bit GDDR5 PCI-Express 3.0 ATX Video Card, model no. RX 480 GAMING X 8G, for $269.99. This $20 mail-in rebate drops it to $249.99. (Amazon charges the same after rebate.) With free shipping, that's the lowest total price we could find by $20. It features three modes with at least a 1,266MHz core clock and 7GHz memory clock, 2,304 stream processors, DirectX 12 and CrossFireX support, and HDMI, DisplayPort, and DVI outputs. Rebate ends October 31.
Note that you'll also receive a coupon with this purchase that's redeemable at AMD for $20 off Battlefield 1 Early Enlister Deluxe Edition for Windows or Battlefield 1 Deluxe Edition for Windows.