Honestly my idea of the ultimate street setup on an STI is
Uprgaded TMIC (perrin,TXS, APS,SPEARCO etc. NOT ebay junk)
Aftermarket up pipe with flex section
Ported/polished exh manifolds with Grimm crossover pipe
Faster than stock spool, MUUUUUCH wider powerband (it will carry power easily 2k further towards redline, the VF39 falls on its face around 4500 and is useless by 5500, the 18G will carry really good power to 6000 and be useable to a 7000redline)
Not enough power to really make the motor unreliable (reliability on a modified motor is relative) and while its going to be a lot of power, a LOT more than a "stage 2", its not enough to be nearly as dangerous in the hands of a non professional driver.
And it will be 50X more rewarding to drive around town than a Green would ever be. I have yet to drive an STI with a green that I didnt hate around town. Positively gutless under 3k. GT30-35 cars are even worse. Starting in first gear from a 2000rpm roll, it would likely take to mid 3rd gear for a green/fmic car to catch the 8cm 18G/tmic car.
If you are more of a power hungry type but still want a nice daily driver, a TD05-20G 8cm is another GREAT choice. Its what I use. Its not as nice around town as the 18G was, but its still AWESOME. At no point in the powerband do I have less than or even equal to stock power. It should be noted however that I run an EWG so I do get a bit faster spool than you would with the IWG. And I dont recommend an EWG for a daily driver. I personally am an obnoxious guy and like the noise
And I am power hungry, with years of high powered cars and subbies under my belt.