Average overclocked speed for Celeron II

[UOVS]

I currently own a Asus P3V4X motherboard and a Celeron 533 PPGA. I want to upgrade to the newer FC-PGA Celerons. Should I buy a Celeron 633 or 667? What overclocked speads should i be able to reach with my new processor? Will the Thermaltake Golden Orb which I have on the PPGA Celeron fit and will it provide enough cooling for overclocking?

Thanks