Choose a WD / Seagate HDD from ebay within 5K, use the 20% off Citi coupon to get 1K off... At current prices, you can get a 500GB 2.5" drive for about 3.7K. If you can stretch your budget a bit, a 1TB 3.5" HDD will set you back by about 4.5K. Check the ebay coupon thread for more details on the Citi offer.