You bring up a good point about what constitutes a "determined" person, Hal. A well equipped pro isn't going to be stopped, but I'm not as worried about theft as I am about somebody foolish or very young getting hold of one of my guns. A pro with any amount of time on his hands is going to be able to get lots of other goodies too- TV, Xbox, laptop, etc.
In that case, the Gun Vault or even the Stack On would probably be sufficient. Like I said though, make sure to keep the backup keys out of the house, probably with family close by or something, make sure it's securely mounted and set up a schedule to change the batteries. I change mine every 6 months, whether they need it or not, just like a smoke detector. I'm ok dropping a few bucks every 6 months to make sure my gun is accessible when I need it, and not finding out the battery ran out of juice the same night I need it.