another thing to remember is, eminences are rated quite highly compared to what they actually are- they use a different rating system to celestion.
for example, the emi version of a greenback (the private jack, as far as I'm aware) is rated at 50W, while the celesion version is 25 (or 20 for the heritage one).
Something like that. it's likely, in other words, that if the celestion g12H30 is rated "correctly" at 30 watts, that the legend might be more like 70 W, or conversely if the eminence is rated correctly at 100W, the g12H30 might be more like 50/60 watts (all figures there entirely arbitrary and made up to give you an idea).
I think. From what I hear, anyway.