The snorkel is going to give you cleaner, cooler air - won't change the power much at all, but gives you the ability to contemplate water crossings. If that's not your thing, and you don't drive in dusty environments (or in convoys), the exhaust has to be first - you'll get an extra couple of ponies out of that - it won't be much though.
If you're considering heading towards a chip, then consider which exhaust would be better once you chip the thing - have a talk to Robert @ ChipIt before you spend any money. If he says a 3" is better than a 2.75" for the chip, then do that now, so that when you chip it later you won't have wasted any cash.
