I think a true XBOX killer would be an older system with a top of the line E8xxx Core 2 Duo CPU. These systems are very easy to obtain, by buying a used corporate system, ebay and local used computer shops are full of them. It is very important to go with the E8xxx series C2D CPU. Why? Huge 6MB L2 cache. If you wonder what is the impact of that, I did some research. My present system has a C2D E7400@2.8 GHz with 3MB L2 cache. I overclocked it at 3.0 GHz (285MHz FSB) and ran Performance Test 8. At the same 3.0 GHz the E8400 is 37% faster at Physics calculations on the CPU, and using the same graphics card as mine (Radeon HD 5770) gets 22% more performance in 3D gaming for DX11. For DX10, the advantage of the E8400 is just 7% using the same graphics card. Given the fact most corporate systems cannot overclock, it is important to get a top of the line CPU, E8400 and E8500 equipped systems are plenty on the web. Such a system equipped with 8GB of DDR2 and a powerful card like a GTX 750Ti would knock down an XBOX.