With those CPU's to put it simply you just added 2 more cores, the 200MHz difference in speed isnt going to be noticable. The only time your going to see/feel a difference between your old CPU and the new one is when your playing games that are specifically desinged to use multiple cores or in applications designed for multiple cores, like doing 3d rendering, video encoding, and file compression.
But otherwise I guess dipankar is kinda right.
For a real boost in performance, specially gaming performance, you'd need a new GPU in addition to the new CPU.
Otherwise the PC is going to be GPU limited.
it definitely say core speed as 800mhz with the multiplier reading as 4. Sometimes it says the core speed is 2646mhz with the multiplier as 13. If im correct shouldn't the multipliers be the other way around?