epitaphoftwilight

Hello, I am new to this forum and i am looking to buy an Impreza WRX. The sti is freaking awesome with its 300 hp and 300 lb-ft of torque but its a little much on the money side. The basic reason for this post is, i wanted to know the difference in the two other than the 70 hp difference. Could i eventually turn my basic wrx into a sti monster? Thanks in advance for the help.