I think when it comes down to ultimate or final authority, a few things needed to be taken into consideration. God, of course, is the final authority, and we know scripture to be given to us by Him...we are told that all scripture is 'God breathed'. And while God does indeed talk audibly to some people, the ones who experience this are few...usually our 'direct' contact with God comes through the Spirit and his convictions within us.
The problem with putting anything above scripture as final authority comes to us in the handy example of this forum board. How many people would you say, that are here, that claim, absolutely that their interpretation of scripture is the only true one? That person over there claims God actually spoke to him saying this; while the other bloke here says that his pastor/minister/priest said the opposite, so that must be true.
We know from the bible that not all the 'spirits' come from God...that we are to test them. And one things we know for certain...man is fallible and sinful. So how on earth do we reconcile things coming out of man's mouth? There must be some way to know if what that man is preaching is true, or whether that other man really had a message from God, or he's being duped by some other 'spirit'.
We see in Acts, that a group of people, the Bereans, were 'noble'...that before wholeheartedly believing something, they 'searched the scriptures' to see if it were true. This is a great example for all of us. The bible, being God's word, must show the truth, of who he is, who Jesus is, and who we are to live for him. There is nothing wrong in listening to others in authority...be it a priest, pastor or some ministry leader. But before believing them without reservation, we need to 'run it by' the bible...if the message they teach is found in scripture, then their message is one from God. It's a fairly simple thing really, but huge in practical application....because there really is only two things we can be sure of: the bible is God's word, and man, even if meaning well, is fallen. It's like being in a foreign land...Sweden, maybe, and having a translator that speaks a little Swedish, but mostly French. You're really not going to trust every interpretation that comes through that man...not without running it by your handy little 'Swedish to English' book, now are you!!?