A best bet is the HP TouchSmart 320-1050 AMD X4 2.1GHz All-in-One 20" Desktop PC (pictured), model no. QP789AA#ABA, for $629.99 with free shipping. That's the lowest total price we could find by $30, outside the deal below. It features an AMD X4 A6-3600 2.1GHz quad-core processor, 20" 1600x900 widescreen LCD, 6GB RAM, 1TB 7200 rpm hard drive, DVD burner, 802.11n wireless, USB 3.0, and Windows 7 Home Premium 64-bit.
A close price is B&H Photo-Video's $633 with free shipping.