E-PM1 Upgrade to DMC-GM1 Worth It?

[Vsin]

Hi all, I am looking to upgrade from the E-PM1 to a camera with a better sensor. I would like the image quality difference to be noticeable but the main priority would be lower noise at high ISO. The final priority though is size: I'd like it to be the same size or smaller than the E-PM1. That's why I am considering the DMC-GM1. What do you all suggest I do? Pick up the DMC-GM1, the E-PM2, or wait for the next new tiny Micro Four-Thirds? Thanks all!