This is a general question on whether the effects from a spell stack with the effects of a wondrous item that was created with that same spell, in case the item's effect is different from the spell itself.
Example: The monk's belt (DM 240) is a wondrous item created with either the spell righteous might or the spell Tenser’s transformation. The effect is as follows:
This simple rope belt, when wrapped around a character’s waist, confers great ability in unarmed combat. The wearer’s AC and unarmed damage is treated as a monk of five levels higher. If donned by a character with the Stunning Fist feat, the belt lets her make one additional stunning attack per day. If the character is not a monk, she gains the AC and unarmed damage of a 5th-level monk. This AC bonus functions just like the monk’s AC bonus.
Looking at the item characteristics, they are different from the benefits of the spell righteous might.
Now, the wearer casts on himself the spell righteous might.
Does this mean that the monk/cleric wearing the belt will also gain the benefits of the righteous might spell too?
how would it work if some effect between the spell and the item were "the same" and some were not?