First I think you need to decide what you consider light is. Then you need to define what your goal is here. Do you just want something light? Or something that will last as well? You've already said you're not riding competitively so anything under like 1800g should do you fine. Honestly I don't even know if you'd be able to tell a difference really from what you have already. I mean, from a stand still maybe you will accelerate faster, but then what? You'll get to that red light 2 seconds faster?