Todd,
I'd advise against the Performance. My basic rule of thumb on any big decision involving money (buying something, a new job etc.) is "will this change my lifestyle at all?" I would think that $10k (plus tax) would not only put a dent in your finances, but is money you'll miss somewhere down the road where you could use it for something else, or better yet for savings for a rainy day.
The bottom line is that like someone who has never eaten certain foods (like people who are kosher and don't eat lobster or pork), you really won't know what you're missing with the Performance. For friends who have asked, I basically tell them that unless they truly have $10k to spare, it's not worth getting the Performance.
Think about it another way -- what's the difference between a mid-level and high end Mercedes or BMW? In other words, try driving a BMW 535 and a 550 and see if you notice a HUGE difference, and if that difference would actually make you want to spend the extra money for the 550. I realize it isn't exactly analogous, but unless you are a really serious driver who is going to really push the car to its limits, I suspect you will never, ever "miss" the added juice of the Perf car.