Microsoft Store cuts up to $500 off a selection of items in its sale section. Plus, coupon code "SAVE100" takes an extra $100 off select items. Better yet, all orders qualify for free shipping. A few best bets, with prices after coupon:
Best Buy offers the Asus ROG Intel Haswell Core i5 Quad 3.2GHz Desktop PC, model no. G20AJ-B07, for $729.99 with free shipping. That's the lowest total price we could find by $59. Features include an Intel Core i5-4460 3.2GHz Haswell quad-core processor, 8GB RAM, 1TB 7200 hard drive, NVIDIA GeForce GTX 750 2GB graphics, 802.11ac wireless, Bluetooth 4.0, and Windows 8.1.