Another 2c
Big difference between an STI and a WRX I would think... the WRX is a mass market performance car, the STI is a street legal race car.
The road is not a race track. Could get a WRX and a race kart/dirt bike/quad bike/jet ski with the difference to an STI.
But if you have your heart set on an STI, you should go for it. Could buy an older one to see if you like it then change up to a newer WRX/STI depending what you decide.
This one looks well maintained, don't know about prices
http://www.trademe.co.nz/Trade-Me-Motors/Cars/Subaru/WRX/auction-240876246.htm