dream engine mods

Say u had $1600 to spend on the engine alone. NONE more than that amount. (no turbo, supercharger, or nos) what would u get to slam this engine??? i ask this cause this is my situation and i need some advice. These are my current mods after having this car only 2 months: halogen headlight, halogen fog lights, 17" wheels and tires, 1.5" lowering springs, Ractive muffler, and double deck alluminum spoiler.