i have a 99 uk turbo with, vf28, fmic, 550's, k&n, fpr, walbro fp, decat system, apaexi pfc, avc-r, uprated headers+up-pipe., runnign 318nhp-303lb

now i am happy but always wanted 400bhp not sure were the figure came from but always had that in mind. so i guess the next step to be safe as i woul dnot want to worry about the engine giving up would be internal rebuild plus supporting mod upgrade or 2.5ltr plus mod upgrade.
along with a gearbox swap to 6 speed as i would want to know that i can use it not have to be gentle and worry everytime i put my foot down in 3rd that it would not destroy the box.

but what i cant decide is, is it worth doing it to my uk turbo or sell up and do it to a classic sti, i assume there is no difference as the engine and gearbox would be changed along with suspension so what would the sti offer over the uk turbo as a base car other than

different interior, lighter bonnet and bootlid as if i am changing the above what else is left that makes the sti a better car?

or surley would it make no difference at all