PCConnection.com has the Acer Core 2 Quad 2.5GHz Desktop PC for $400 w/ free shipping.
The Acer Core 2 Quad 2.5GHz Desktop PC features: An Intel Core 2 Quad Q8300 2.5GHz quad-core processor, 4GB RAM, 750GB Serial ATA hard drive, dual layer DVD burner, integrated video plus one PCIe X 16 slot, Gigabit Ethernet, and [...]