Correct me If I'm wrong..
but Spell Power +1 , +2, or +3 is much more powerful than simply raising your spell DC.. it also gives you a bonus to caster level checks to overcome SR.
Getting Spell Power +2 is the equivalent of getting Spell Penetration **AND** Spell Foci in every school you can cast.
A silly Wiz 15 / Acm 5 with Greater Spell Penetration rolls caster level checks as if he were level 30. Hopefully MMII will have higher SR's... because unless i'm missing something, only Solars and Tarrasques can possibly resist.. and even then only on a 1, or a 2.
Which is why I too am becoming an Archmage one day. (with a +4 Headband of Int- hey... if I can make one, I can wear one.)