Then the highest for you is the X2 4800+ I believe. I wouldnt do it, simply because theres not a huge increase in performance between the two, you should try overclocking yours until you decide to get an Intel Core 2 Duo.
completely agree just wanted to here it from some one else looks like it will have to be a complete rebuild to change to Intel Core 2 Duo
thanks you just made me spend alot of money.