>>2580607So you're saying you're going to use Sigma AF lenses intended for Canon in MF on your Sony? What's the fucking point of that? Get native Sony/Carl Zeiss lenses, in any other scenario this will be just gearfagging with no usability.
So 600D is noisy? Doing what? I imagine only astrophotography or event photography indoors which could be limited by your camera ISO.
Is it too big? Use it with smaller primes, it will be rather small. Sony with zooms or really fast primes still gets big.
I don't see your ideas as a consistent approach to gear. It seems that buying new stuff will not bring you better pictures.
Eitherwise you should elaborate what do you shoot and what troubles you.