A new start

Well with direct x 10 right around the corner I would like to get my computer setup to handel the next generation. Now I think all I should do is upgrade the mobo and the proc but I'm not sure what I should look at. I hear a lot of good things about opteron but how exactly it compairs with athlons. The specs that I have listed is my current stuff so could I get some suggestions?

Oh I'm running on about $500.00 budget here so I need to stick close to that.