What is the best £500 gaming machine you can buy today?

This only includes the tower, no monitors or OS, ect. 

dude, here is what i got for you :) http://pcpartpicker.com/p/D5IY

this build can play any games. Older games at ultra settings and games like Battlefield 3 of Far cry 3 at Medium-High setting with good frame rates ( between 30 and 40 fps)