If you have the $$$ to spend, get the GSR. The registration and insurance will be higher, but you have a better platform to build upon. However, if you want a car that is relatively more rare AND will save you some $$$, get the SI. Later on, you can build a B18C block and swap it in the SI. This way, you will have the better flowing head (B16) and the better torque block (GSR). Then, since it is built it will be well suited to turbo. Plan on replacing tires often and having a lot of fun doing so.