Sandman's pretty much covered all of my points.. The weight difference between an SVT (with the Turbo kit) and a Cobra or C5 isn't that much, 400lbs at most. I'll still stand behind my claim that the RWD and torque advantage will more than make up for the weight penalty, not to mention where in the curve the HP is being made.
My price comparison is based on the initial price of the SVT (since most of us bought the car new), plus the cost of the Turbo, Quaife, and installation. You're right at the price of a used C5 or 99/01 Cobra. Still no contest. Or you could buy a used 3000GT, 300ZX, or 2nd Gen Eclipse Turbo, with about $10K left over to make it RIDICULOUSLY fast. Or even a moderate mileage Supra. Or even a pimped out turbo Civic with NAWZ! :>
Keep trying to justify it, but unless you plan on keeping the car forever, it doesn't make sense. You'll be kicking yourself after you blow the motor too, in famous SVT fashion. Warranty? What warranty?