also, while the original thread was dealing with animate dead from a cleric/wizard... would it change anything if it was summon monster from a sorcerer/wizard? one being divine/arcane and the other being arcane/arcane...
The specific spell makes no difference to the question asked.
You would have to specify which class your initial spell applied to, as you can only replace it with spells from that class, but I don't see any restriction on which class you actually cast it from.
You choose summon monster II. If you cast summon monster II you get +2 CL. the feat doesn't check which class cast it.