Sudden Empower( Complete Arcane, p. 83)
You can cast a spell to greater effect without special preparation.
Any metamagic feat,
Sudden Quicken (CAr) ,
Once per day, you can apply the effect of the Empower Spell feat to any spell you cast without increasing the level of the spell or specially preparing it ahead of time. You can still use Empower Spell normally if you have it