celerons | pentiums

[chael at southgate.ph.inter.net]

A newbie question: 
I don't know much really about the differences of the two processors except that (I think) Pentiums has a multimedia extension and Celerons has NOT. So, is there a significant gain (if any) in performance if you use Pentiums than Celerons on FreeBSD that is running as say a cache/proxy server? If not, is it right to think that the extra money we shell out for a Pentium is not really worth if we're not gonna be using it on a graphical environment with media players, et al? 

Thanks.