Performance enthusiasts have long appreciated the Sea-Doo RXT-X. After all, it's a boat built for speed and handling, and featuring a touch of aftermarket-inspired extras. That it hits 67 mph on the top end, turns on the proverbial dime, and leaps out of the hole with arm-stretching acceleration is almost expected. That it does even more than the expected, however, is what makes it special. The X Factor What exactly qualifies a boat as an X model? For Sea-Doo, the answer is a series of race-inspired tweaks and add-ons, the most noticeable of which is likely the craft's dramatic, X-sha...