Newegg has the Hitachi GST H3IK40003272SP (0S03355) 4TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive for $300 - $50 off with coupon code EMCJNJB27 [Exp 10/20] = $250 with free shipping. Features SATA III 6.0Gb/s interface, 7200rpm drive speed and a 64MB data buffer cache.
3 Year Warranty on this drive. I picked up 2 of these from Fry's a few weeks ago for $199.99 + CA sales tax.
make sure you back up!