I suspect that you will outrun the 4850, or certainly achieve plenty fast framerates, before you hit the limit of that E8500. I run my E8500 at 3.8GHz for CAD everyday. In apps that don't use multiple cores it will match or come close to matching any cpu that you can get today. In such apps my CPU at 3.8GHz will equal the performance of an i5 or i7 at 3.5GHz. Yours at 4GHz would equal an i5 at about 3.7GHz, and some of them don't run any faster than that.