As an addition to what J.F.R. said, I would mention that I just love shooting with the Nokton 25mm f/0.95 and that it does indeed go some way towards addressing the lowlight gap.
But I would NOT shoot ISO 3200 on the GH2 for normal narrative work, just documentary-style stuff, etc.
I almost always wish I'd shot anything that's at ISO 2,500 or above at a lower ISO.
GH2/3 is not the camera for such high iso work.
Look towards the Mark III or more expensive cameras.