Get the latest BIOS and QX6800 SLACP is the best CPU. 8GB DDR2 800 RAM (low density). That and a single slot single fan GTX750 is the basic bolt on setup (a dual slot GPU will need the bracket cut in 1/2 to fit and sometimes trimming the cover a little.). Aftermarket PSUs fit. If you won't be overclocking any QX6800/6700, or Q6700 will work. D9729 is a bolt in heatpipe cooler. Look at the link in my sig. to see what a maxxed out E520 can do. If you click on the image there it will take you to the QX6800 rankings page.