I would say upgrade your system. The ls is a powerfull engine that works great with a turbo. If youre going to spend 3500- 4500 buying a gsr or a type-r engine,might as well spend 2000-2500 to turbo your ls. A type-r or a gsr would give you 170-190hp while the turbo ls can give you up to 220hp and still have it be a daily driver. The cheaper ways to improve your engine's performance would be Intake headers and exhaust; but if you want some serious power look into turboing your Ls, trust me it's worth every penny.