I'm pretty new to the game, and was wondering how casting modifiers effected dispelling, if at all. Here's what I mean; lets say my opponents caster needs a 3+ to cast 'whatever' and has an item that gives him +1 to casting rolls. He rolls a 2, and gets his plus +1, the spell goes off. Do I need a 2+ to dispell or a 3+?
From another angle I have a magic item that put my opponent at a negative to cast (DoC Great Standard of Sundering, -2 to casting for a chosen lore). My opponent needs a 6+ to cast a spell, rolls a 9, still gets off at a 7 to cast, but to I need a 7 or a 9 to dispell that spell?

Looked in the rulebook and the two FAQ's couldn't find anything on the matter, any rulings, opinions, or direction?