Not sure if anyone will get any use out of this, but I found a gold orb I didn't see in the guide on mission 17, if you go into the church thing at the end of the level where you get the item that makes nero have the ability to use grim grips. you must go out the door you would use if playing through level 2 as nero. to get up there as dante, stand on a pile of rubble and hit dt then triple jump. once outside the door you should be able to see it.
sorry to be long winded.