the b16 will be the cheapest swap that will make a decent amount of power. the b16 is fun because you can beat on it and beat on it all day, everyday and not worry about it. the gsr is a great swap too. actually an ls b18b or b20 with a b16 trans is a great swap. decently quick, good torque and great for boost later. slam it! get some ground control coilovers