[G4] Processor upgrades... Worth it? Fast? Groovy, even?

[Brian L. Matthews]

>Having some L2/L3 cache is significantly better than having none, as 
>some machines did. L2 cache is on the processor chip itself and 
>usually runs at the same speed as the processor. The L3 is on the 
>processor daughterboard and usually runs at half or one-third the 
>processor speed. Although you didn't say, I'm sure that the 1.2/1.33 
>GHz processors would have L3 cache, which is almost as good as L2. 
>You would certainly notice a dramatic difference when you double 
>your processor speed. A friend of mine upped his machine to a 1.33 
>GHz and the difference was eye-opening.

Which leads to my question, which company's processor upgrade should 
I go with? I've got a 500Mhz G4 Sawtooth. I believe PowerLogix, OWC, 
Giga, and Sonnet all make processor upgrades for my machine, and they 
all sound good from the companies' web sites, but I'd like to hear 
some real-world experiences before dropping what in all cases is a 
decent chunk of change.

Thanks,
Brian