Newegg offers the refurbished HP Debranded Intel Haswell Core i7 3.7GHz Desktop PC, model no. TS-151-018-W8PRO, for $659.99 with free shipping. That's $140 off and the lowest total price we could find. Features include an Intel Core i7-4820k 3.7GHz Haswell quad-core processor, 8GB RAM, 2TB hard drive, DVD burner, Blu-ray drive, and Windows 8 Professional 64-bit.
A 90-day warranty applies, although it's not clear who backs it.