Gateway LX6810-01 Desktop PC with Intel Core 2 Quad at 2.33GHz for $569.00 shipped.  Here is a screenshot for your reference.  Alternatively, it is available here for $589.99 shipped.  This system features an Intel Core 2 Quad processor Q8200 at 2.33GHz, 8GB DDR2 RAM, 640GB hard drive, NVIDIA GeForce GT120, built-in HDTV tuner, dual layer DVD burner, 15-in-1 media reader, Windows Vista Home Premium (64-bit) with SP1, and more.  Note that this system is also eligible for Free Windows 7 Upgrade.  As a comparison, Best Buy sells it for $779.