Price wise they will cost me the same (and below dealer list).
As for making the 350 faster, that's what I am looking to get away from. I've had my run with modding for now and moving onto other things (restoration projects).
Overall I'm just torn right now. One thing that I am concerned with about the STI is cost of ownership. There's just soo many electrical systems in there that I don't want to get stuck with a problem child once the ESP runs out. The 350 may not be any better but I do know the sales manager and have been at the track with the owner a few times (I actually went for a "test" drive in his own 350 a few weeks back)