One thing to keep in mind is that most extended warranty plans only come into effect when the manufacturer's warranty has expired. Since the STi will have a 3/36 B2B warrant and a 5/60 LPT warranty, a 7/100 mile warrenty may only be in effect for 2 years. I would consider the odds of repairs in excess of $2500 happening in that time span to be small. Especially when you get into the fine print about what the warranty actually covers.
The bottom line IMHO is that extended warranties are serious money makers for the people that sell them, and that happens for a reason. Statistically speaking, you'd be better off taking the money you'd spend on a warranty and putting it into a savings for 5 years (assuming your standard warranty will cover repairs for 5 years). If you're going to be financing the cost of the warranty your making the odds of breaking even on the purchase even worse.
The one intangible that an extended warranty buys you is peace of mind that you won't have to deal with any unexpected maintainence costs for a couple years longer. For some people this is well worth the money alone. Also, in my experience purchasing an extended warranty may come with other cool perks (better loaner car, discounted routine maintainence, etc.) that can make the deal more attractive if you take advantage of them.
Perhaps someone from a finance department can chime in with what kind of pricing and fine print we can expect on different options.