check latest issue of Sport Compact Car
STi vs. 3 WRX tuners...
the 3 tuners ranged from as mild as they get mods to as expensive and rediculous as they come mods. the cheapest had ECU work, turbo back, suspension upgrades, big brakes, wheels/tires.
the most expensive had most mods you can purchase today for WRX. it cost about $55,000 to put together... and was slowest from 0-60mph while producing by far the most whp of all the cars, including the STi. because it had a dual plate clutch and huge boost numbers,,, the clutch didn't allow for a launch at high rpms... so it was slow until it was over 4000rpm... then generating huge huge whp above 4k rpm...
the middle of the road was equipped with Vishnu stage 4, R compound tires, big brakes, and suspension. It bested the STi in every category slightly and extremely similar whp numbers to the STi on the HKS dyno. the lowest model was the only one to still have stock turbo and while it did lose to the STi and Vishnu, it did fair quite well over all, considering a moderate cost to make the improvements that were made.
The SPI motorsports, $55,000 in upgrades, was said to be likely to have whooped all the cars if it had kept its stock clutch (allowing for high rpm launches)... dyno'd at over 330whp.
And the price to upgrade in the end to the Vishnu stage 4 with the brakes and suspension was actually $1500 less than base price STi... so yes you lose the warranty and the interior, but you gain a slight performance edge over the STi... Its a matter or preference... i'd probably take the STi for the sake of a having a real cool, rare car.