Do you mean, what are the best settings you can get in games with the HD3850??
If so, I'm sure you will be able to play Crysis for example in Medium settings with the X2 4000+ and getting decent FPS. Not sure though maybe you can get more. You won't regret it, it is a great card! Try it then if you feel you need more speed, more RAM doesn't hurt and you can always upgrade your CPU.