S5 IS replacement
You should also consider Powershot G15/G16 and maybe upcoming G18 as middle station between S and G1X cameras. For general purpose, those are just a tad better. For low light, fun and serious photos, those are miles ahead. If you really want to shoot seriously, I´d sacrifice that need of weight and considered G1X II or even small MILC/DSLR. The reward in image quality and capabilities is HUGE. If you´d like to have just better gear, I´d consider Powershot G16 or Olympus XZ-2. Very good cams and still about being pocketable (big pockets).
Why does he do it?