If you modify a spell with a metamagic feat, does it count as a higher lvl spell for purposes of using a rod on the same spell?
And a follow-up quest if the above is correct - you use want to use a metamagic rod on a spell of 3rd lvl that's been modified by a metamagic feat, can you still use a lesser rod, or you need more powerful ones?
Spells modified by a metamagic feat use a spell slot higher than normal. This does not change the level of the spell, so the DC for saving throws against it does not go up. Metamagic feats do not affect spell-like abilities.
Fireball is still a 3rd level spell. It just requires a 6th level spell slot when maximized.
So a lesser rod should be kosher you just have to avoid putting enough meta-magic on it to raise beyond a 9th level spell slot.