I don't think those older 775's can take DDR3.
My guess, looking at those specs, is that he recently upgraded his video card from something like a 8800gt to the new 460 and isn't seeing much in the way of fps increase.
From my research, looking to upgrade my 9800gtx+ sli setup running on an evga 780i board, I needed to get an i3 or i5 to make use of the new video cards (6850, 570, etc). That is probably what you'll have to do as well. So keep the 460 and use it in a new build.