It wouldn't add anymore weight as you are just replacing one part with another of a different type. The bigger power will come from the higher compression and the better cams.
Of course if this starts happening the used SVT cams will become very valuable.

As far as a step in the wrong direction? If you are stuck with a certain type of car, there isn't anything wrong with making it faster.

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black