I got fed up with my spells constantly being shrugged off a while ago, so now I usually focus on sonics and force effects. And thankfully, my DM allows us to take the 3.0 energy substitution feats (including sonic).
Wow, Aelryinth, any chance you could spoiler big AP reveals like that in the future? Some of us are still playing through those two...
Nothing a Knowledge check couldn't find out for you.
As for Legacy of Fire, if you go into the last encounters expecting a freezing-fire cakewalk, you should get hammered. Conveniently, the AP gives you the method right on hand to neutralize the enemy defenses.
===Aelryinth